Triton (T) class Submersibles (1937)

The Royal Navy’s T class (or Triton class) diesel-electric submarines emerged in 1935 on paper to replace the early interwar O, P, and R classes. This was the start of a very long production unding in 1945, with 53 boats made. They played a major role for the Royal Navy, making the bulk of WW2 oceanic submersibles. The smaller “S” and “U” class, even more numerous were light submersibles mostly deployed in the Mediterranean whereas the T class were designed for distant stations across the Empire, notably in the far east and Asia.

Four later were passed on the Royal Netherlands Navy (Zwaardvisch class). They were a quite advanced type which proved to have a very long service (and heavy losses) maintained until the late 1960s after being streamlined, so to counter the growing Soviet submarine threat. The last one was disposed of in 1969, moored as static training submarine until 1974 while another served with the IDF Navy until scrapped in 1977. Note: Due to the number of boats this post will be only on the first group, Triton. There were also the Group II 1940 programme (Tempest) and Group III 1941-42 Programmes (Trespasser) seen in future posts.

HMS Thorn, Group II, 1940 programme, bow view. The T class were not the most gracious submarines around, but they were tailored for a massive ten torpedo forward volley.

Development

1922-30-35 treaties and conferences

The design of what the future “T class”, the largest operational submarines of Great Britain during the second world war, started in 1934 to create a replacement for the earliest British interwar submarines, namely the O, P, and R classes. Indeed reports piuled up on their use and the admiralty now had a clear idea on how to avoid issues of the past;

These large subs proved mechanically unreliable, too large and unwieldy, slow and overcomplicated to operate. The Washington Naval Treaty of 1922 required all these submarines were to be retired after 13 years of service which was the main factor, meaning the Oberon class was scheduled to be paid off in August 1940, meaning with an average time from design start to commission, at least five years. Work for a replacement class thus started in 1934.

There was another hitch: The 1930 London Naval Treaty hardered the 1922 treaty and further restricted British submarine to a total tonnage of 52,700 tons, with an individual surfaced displacement of no more than 2,000 tons regardless of the type, maximum gun armament of 5.1 in (130 mm). The USN in the 1935 London Disarmament Conference argued even for a limit of 1,200 tons, but this was rejected by the British Admiralty as make their Grampus-class mine-laying submarines illegal.

The Admiralty proposed again a limit at 2,000 tons, hoping that rival naval powers would make fewer but larger submarines based on national pride and easier hunt to down than score of smaller submarines. The Conservative government of Stanley Baldwin went even further, proposing an outright banning of submarine, or a 250 tons limit. The Admiralty argued that no other power would accept this as their own submarine fleets were seen as vital core concept. They would never accept such strict limitations. Instead the admiralty for a repeat of the P class.

Basic requirements setup (1934)

The O/P/R classes initially were designed with the Pacific in mind, compansetaing for the low numbers of cruisers and capital ships and better suited for more restricted and shallow waters. They were designed to hunt down the Imperial Japanese Navy capital ships due to the absence of a battlefleet. They acted, as in most navies at the time, as a local deterrence. The planned replacement, called “Repeat P” thus needed at least a similar endurance while being easier to maintain and being smaller to match future treaty restrictions. 1,000 tonnes surfaced (the equivalent of a standard isplacement for surface ships) was retained as a baseline for design.

But to draw up future requirements it was advanced that twenty submarines would be ideal, making for a total tonnage of 20,000 tons (On 52,700t global). Rear Admiral of Submarines Noel Laurence, a veteran, awared WWI sub commander, argued also for a stronger torpedo armament that would gave a greater firepower in a single volley rather than more reloadable torpedoes. He argued that penetrating the Japanese destroyer screen would be difficult and thus, a larger salvo with longer range torpedoes was ideal. They would be setup using only ASDIC data to find a firing solution.

On 27 February 1934, the Director of Naval Construction (DNC) was Sir Arthur Johns. Her asked to study designs for a 1,000 ton displacement “patrol submarine” and initially two DNC designs were drafted, called DNC ‘A’ and DNC ‘B’ used as base for discussions in November 1934 and create a staff requirement. The base was an armament of six internal 21 inch torpedo tubes (reloadable), two external tubes (not reloadable), one 3-inch or 4-inch on deck depending on stability calculation, and a range of no less than 4,000 nmi at 11 knots, or a 28-day patrol moe or less related to 5,500 nmi at 11 knots.

Submerged endurance was setup at 15 hours at 2 knots or eight hours at 5 knots for the final approach, maximum submerged speed of 9 knots, surfaced speed of 15 knots and diving depth of 300 feet. Rear Admiral Laurence suggested also a variant fitted with a double hull for greater survivability under attack but this was rejected by the DNC cito,ng the lack of experience in this matter and favouring of a more conventional saddle tanks/pressure hull combination.

1935 Final Design and acceptance

T class, likely Group I src

In early 1935, the still named “Repeat P” design was to have a smaller displacement than 1,000 tons to comply with the 1935 London conference limitations. Design ‘C’ as drafted sacrificed machinery space and managed to get the surfaced speed reduce to 14.5 knots, surfaced endurance to 8,600 nmi at 8 knots. Design ‘D’ went further and eliminating external fuel stowage which was a leak sourced anyway on previous O, P, and R classes for pressure hull internal stowage, but all argued that it was impossible to meet below 1,000 tons without unacceptable reductions and thus, it was raised up to 1,075 tons as a compromise.

There was a slight reduction in length and fresh water diving requirement also to have a lighter hull, and dur to the emergency, the final design was agreed upon in May 1935. On 24 June 1935, “Repeat P” was swapped to the next letter “T” and by 3 September 1935, the name “Triton” was selected for the lead boat, with final approval coming on 13 February 1936. In between the “repeat P” already had been provisionally included and authorized in the 1935 naval program, secured by law at the house of commons. The admiralty then invided for tenders Vickers, Cammell Laird, and Scotts on 5 December 1935. On 5 March 1936, two years after the process started, contract was awarded for the Triton batch to Vickers Armstrong under the 1935 Programme. She was the only one ordered that year in the hope to find construction issues and correct the next ones. Later Chatham NyD was contracted for the third and fourth batch.

Construction planning: 1935, 36, 37, 38 programmes

These 15 pre-war submarines of the “T class” were ordered under the Programmes of 1935 (Triton alone), 1936 (next four: Thetis at Cammell Laird (later Thunderbolt) Tribune at Scotts, Trident at Cammell Laird, Triumph at Vickers), 1937 prgramme (next seven: Taku at Cammell Laird, Tarpon at Scots, Thistle at Vickers, Tigris at Chatham, Triad at Vickers, Truant at Vickers, Tuna at Scotts) and programme 1938 (last three: Talisman at Cammell Laird, Tetrarch at Vickers, Torbay at Chatham). The names for the T class were a repeat of the destroyers names of WW1 and not related to anything marine in particular, apart some exceptions. “Tigris” was a Mesopotamian river, Taku and Triad were Chinese-related (where they were supposed to serve, notably from Hong-Kong) and only Triton (fitting as the son of the sea god Poseidon and the sea nymph Amphitrite, with a fish tail and human body), Trident, and Tuna were sea-related. Torbay is a famous bay in Devon.
Construction time on average was two years. This was of course improved in the war years. HMS Triton took 2 years and 4 months, HMS Torbay one years and two months. She was the very last launched, in January 1941. Only thre of the class were completed when WW2 broke up an the consequence was to free tonnage from all treaties. Soon a Group II (War emergency 1940 program) planned sixteen “repeats” launched in 1941-43, completed in 1943 (see later).

Design of the class

The design of the T-class submarines was dictated by at first their very large forward torpedo salvo and long patrol endurance for the Pacific while styll comply with stringent treaty restrictions. These were extremely challenging requirements and so compromises led soon to modify operational experience before and during the war, leading to three diverging groups. The next A class was a return to a treaty-free ideal Pacific long range submarine.

Hull and general design

The six bow tubes were not different but the bow was bulbous and peculiar, notably to accommodate the external forward torpedo tubes, with the original bow shape later was found affecting speed while surfaced. Two of the Group One boats, Triumph and Thunderbolt in fact had their external bow tubes deleted during refit and this resulted in a finer bow shape.
The Triton class were still of well mastered riveted construction as riveted hull proved remarkably strong and indeed, on tests these boats exceeding their rated diving depth of 300 ft (91 m) in combat missions, Tetrarch even survived a 400 ft (122 m) dive on 23 April 1940. Welding was applied from Group III boats and allowed greater depths.
HMS Triton had a very high open bridge and was found to plow a lot, with a lot of draught. It was reworked for the remainder of the class, with a new shape, but even with the new breatswork, the lower bridge and gun crew were exposed to seaspray and splashes in heavy weather.
Some Group One boats had also cab-type bridge, subsequently standardised for Group Two boats. But it was reverted later to open bridges as greater visibility was more important than the better habitability. Group III returned indeed to these.
Also, brass for the CT was used instead of steel to prevent interfering with the magnetic compass, but this causes structural weaknesses. It proved impossible to fit heavy machine guns due to the vibrations, either Vickers quad 0.5 which would have been ideal at the rear platform, or a twin 0.5 Browning HMG. But the recoil was just too much. Instead, 0.303 Vickers, Brens, Lewis were preferred, but they were a poor answer to 600 kph capable fight bombers in 1942. At last in 1944 sime received 20 mm Oerlikon cannons, which recoil was well buffeted enough to cause minimal vibrations (see later).

The triton class had eleven main ballast tanks and two auxiliary tanks for adjusting the trim, as well as five compensating tanks for adjusting to changes in water density (tropical, northern/Arctic). Some were usabled as stores in the first leg of the tip, especially packed food. The bow Q tank was used for diving quicker and rapid changes in depth. Two main tanks were converted into fuel tanks later in Group 3. Diving time at 50% buoyancy was jusged good by British standards, with 30 seconds dive time.

Powerplant

Cutout of the Group II src
The Triton class used various diesel engines, moslty yard dependent. Vickers-built boats had of course Vickers engines, Royal Dockyards boats used Admiralty diesel engines, Cammell Laird boats used Sulzer engines and the Scotts boats (prewar) even used recently purchased German MAN supercharged diesel engines. In all cases, this power was passed on to two shafts with triple bladed props, and each diesel was rated for 1,250 brake horsepower (930 kW). Top surface speed was 15 knots (28 km/h; 17 mph) in normal use. Triton even achieved on trials, light and in good water conditions, 16.29 knots (30.17 km/h; 18.75 mph) and this was never repeated by any of other T-class. The average on trials was 14–15 knots (26–28 km/h; 16–17 mph) and in mission depending of the weather on the Triton class, it could fell rapidly below 10 kts, improved in heavy weather for the next groups.

The Vickers diesels were 6-cylinder 4-stroke 1,250 bhp injection engines that became widespread in the T class. They proved to be very reliable, albeit less advanced than MAN diesels, which were however a bit finnicky. Thes could continue running even if one cylinder failed. The enegineers just had to disconnect the faulty cylinder from the crankshaft. It was well appreciated by captains when breakdowns occured, as to not being found dead in the water.
The 12 boats from Royal Dockyards and their Admiralty diesel engines had the same reliablility even though they were more complicated and les eazsy to maintain, but they offered the same advantages of flexibility.
MAN diesels were high-end products, ordered in 1938 when relations with Germany were still good, but they proved troublesome. They ended built under license and still neded parts and expertise in Germany so that was out of the window when the war broke up. By 1943, just two T-class, Tuna and Tribune ran with them, and were relegated to training use due to their complicated maintenance and poor reliability. In fact they were banned from the far east in March 1944. The Cammell Laird used Swiss licence-built Sulzer 2-stroke engines. They were not always well appreciated, working well on Thrasher and Thorn (Group II) but having issues on others. At full speed they were fragile, with cracked cylinders rings and blocks.

Submerged speed counted on the Triton class or a massive 336-cell battery ensemble. They passed on their power to two 1,450 bhp (1,080 kW) Laurence Scott electric motors, chosen for all T class. They managed to give an endurance of 48 hours, at just 2.5 knots (4.6 km/h; 2.9 mph) and one hour at 9 knots (17 km/h; 10 mph). The battery however proved vulnerable to shock damage from concussion caused by depth charges.

Armament

British work on ASDIC led the admiralty to believe other nations developed similar systems in secret, and that played on the was the armament was composed. Facing detection and a robust ASW counter-attack the tactic defined was a long range approach below periscope depht and using ASDIC. Inaccuraces being the result, the planners included a large salvo of eight torpedoes. It was also assumed that international treaties would prevent unrestricted and so anti-shipping warfare, so that the T class were reserved to hunt down warships only. Against valuable assets of the enemy, all captains knew they had only a single window chance to attack. A large salvo was desriable, and from four-six usually fitted, no less than ten-torpedo tibes was decided for the pre-war T-class. It remained the largest ever fitted to any operational submarine, as all were launched forward. Relading was a secondary matter.

However hull constraints meant only six could be fitted internally of course of the 21-inch (533 mm) standard, in the bow, fitted with bow shutters on thr Tirtons to reduce underwater drag, but they were prone to jamming from flotsam and abandoned for Group II-III.
The loss of Thetis on trials was due to the unintentional opening of the rear door of a torpedo tube while its bow cap was open. Thuis to avoid this in the future, all submarines in construction were given a special safety feature, the “Thetis clip”. It only opened the rear torpedo tube door by a fraction if the bow cap was not in place, showing an immdaite leak and measures to be taken. There were six reload torpedoes in the torpedo stowage compartment at the bow only. The remaining tubes were loaded at port only. The reloading process was of course fully manual and could take 5 minutres per tubes ever for a trained crew. However a semi-automated loading system was tested on HMS Triumph in 1939, after another earlier test on the old HMS Grampus. It was not adopted as underpowered. No effort in wartime was done to get one.

The four external “E-type” 21-inch torpedo tubes were all forward-facing, iin the piter hull in order to avoid compromising the structural integrity of the pressure hull. It prevented maintenance, reloading, but also withdraw the torpedo once in the tube in case of misfire, stil a hazard due to the percussion cap. These tubes angled were downwards at a 5° bow angle but 0° on Triton. Two tubes were in the bow, two amidships at the base of the conning tower and the bow caps were opened manually with great time and effort. Being outer tubes they were also prone to damage. Two had them removed during reconstruction.
Debate over the introduction of stern torpedo tubes raged prewar, and their effectiveness was mostly considered to be doubtful while take up valuable space in the pressure hull. Wartime experience changed that perception. Commander Anthony Miers of HMS Torbay caomplained about it as he missed several occasions. There was no point turning the boat to face a target that would be once spotted, far away. Eight Group 1, Taku, Thunderbolt, Tigris, Torbay, Tribune, Trident, Truant, and Tuna were later thus retrofitted with an eleventh external torpedo tube rearwards in the outer hull. This soon became standard as an easy modification.

10x 533 mm Torpedo Tubes

The primary torpedo used by the Triton class was the 21-inch Mark VIII torpedo as planned. But quickly it was superseded by the the Mark VIII**. The Mark VIII was the first burner-cycle torpedo in service, studied in 1925 and completed for production and service in 1927. The improved Mark VIII**was used far more than any other British torpedo during the war with 3,732 fired by September 1944 which represented 56.4% of the total of all models. Incredibly it was was still in serviced as late as 1983 for the Falklands war (of Belgrano sinking fame). Their tally in the Mediterranean and beyond was on par with the German G7e in the Atlantic, and US Mark 14 (after corrections) in the Pacific.

This 1,566 kg (3,452 lb) model, 21 ft 7 in (6.579 m) long, carried a 365 kg (805 lb) Torpex warhead and used a Brotherhood burner-cycle engine for a range of 4,570 meters (5,000 yards) at 45.5 knots (84.3 km/h; 52.4 mph) or 6,400 meters (7,000 yards) at 41 knots (76 km/h; 47 mph). It had a greater propulsive efficiency than any contemporary torpedo of similar size. Shortages of the Mark VIII early in the war pushed many T class to be equipped with much older Mark IV models. The latter was a wet-heater 1916 model Weighting 3,206 lbs. (1,454 kg) for 22 ft 7.5 in (6.896 m) in lenght,
with a 515 lbs. (234 kg) TNT warhead, capable of 8,000 yards (7,300 m) at 35 knots, 10,000 yards (9,150 m) at 29 knots or 13,500 yards (12,350 m) at 25 knots. It was slow, but its range was revised in WW2 with a new setup for all Mark IV* to 6,000 yards (5,500 m) at 40 knots and 9,500 yards (8,700 m) at 35 knots.

The Mark VIII was primarily fitted with a contact pisto detonating upon impact until a non-contact magnetic pistol, the CCR (Compensated Coil Rod) was developed and fitted. Hioweger like for the Mark 14 and German models, it gave endless troubles, being withdrawn. Development problems with postwar torpedoes had the VIII lingring in service with the T class, A class, and all diesel-electric subs, even the first British SSNs until 1971 and slow introduction of the Mark 23 wire-guided torpedo.

⚙ specs. Mark VIII** TORPEDO
Weight	1,566 kg (3,452 lb)
Dimensions	21 ft 7 in (6.579 m)
Propulsion	Brotherhood burner-cycle engine
Range/speed setting	4,570 m/45.5 kn, 6,400 m/41 kn
Warhead	365 kg (805 lb) Torpex
Guidance	Straight, initial training setup

QF 4 inch (100 mm) deck gun

All T-class submarines were fitted after stability calculations with a single 4-inch (102 mm) deck gun to supplement torpedoes and for self-defence. Either this was the 4 inch QF Mark XII or XXII which were both interchangeable, using the universal S1 mounting located above the casing, forward of the conning tower. Like older subs and typical of british models, to avoid it being awash with eawater spray, it was placed on an elevated position in front of the conning tower, behind a characteristic breastwork rotating with the gun. This provide room for the crew but less easy traverse.

No armour or overhead protection was provided for it however, due to weight restrictions. However in wartime, Group II HMS Tabard, Talent, and Teredo and others received improvised gun shields from far east depot ships. The gun crew was five. There was a small hatch to access more rounds below in the CT. T-class submarines were allocated 100 rounds of ammunition, that needed to be brough back from below in a chain. This proved insufficient as per combat reports of Group I boats (Triton) and was increased. In fact, in 1945 no reload torpedoes were carried, but more rounds instead.
The Mark XXII equipped the WW1/Interwar L class, Odin, Parthian, River, Grampus, Triton, S and Some of the Amphion (“A” or Acheron) class.

⚙ specifications QF 4-in (101.6 mm) Mark XXII
Weight	2,750 pounds (1,250 kg) barrel & breech
Barrel lenght	160 inches (4.064 m) bore (40 calibres)
Elevation/Traverse	-10° to +20°, 150° either side arc
Loading system	Horizontal sliding-block breech
Muzzle velocity	1,873 feet per second (571 m/s)
Range	11,580 yards (10,590 m) at +30°
Guidance	Optcal
Crew	4-5
Round	Fixed QF 31 Pd (14.06 kg), 35 pounds (15.88 kg) from 1944
Rate of Fire

AA Defence

The standard anti-aircraft armament was limited to three .303-inch light machine guns and even initially Lewis guns as completed. From 1941 onward, Group II-III, these were replaced with Vickers gas-operated (VGO) machine gun, sometimes substituted with a Bren gun if supplies could be delivered fropm the Army. In 1945, all T class that underwent a refit, received a 20 mm Oerlikon AA gun located located aft of the conning tower. The later HMS Tantivy even had two 20 mm cannons side by side, and Tireless was completed with a twin Oerlikon Mark 12A. Terrapin acquired a .50 inch Browning air-cooled machine gun but it was too powerful for the conning tower structure in Brass, easily damaged.

Sensors

Type 129 sonar

A keel-fitted model, 10 kHz as standard frequency. It was first trialled behind a dome at the forward end of the keel of HMS Seawolf in 1937 (S class) and in 1938 adopted as standard, installed on the T Class, U Class, and V Class. It was fitted in a cylindrical cage with streamlined dome underneath the forward torpedo tubes. There was a watertight electric motor inside the pressure hull to drive the oscillator. But the dome would also be reached internally for maintenance, repair or exchange. HMS Torbay had the first trying this, by isolating the fore ends and having enough pressure in the compartment to counteract sea pressure before opening the hatch and withdrawing the oscillator, re-shutting the hatch, with the process later reversed. This procedure was later adopted on all T class submarines and other classes as well.

Type 138 sonar

Because of its location, the Type 129 had a blind stern arc. From 1943 (so for Group II-III) a passive and manually-trained listening hydrophone was added to cover the rear blind arc, complement the more versaitle Type 129. On the T Class it was located in the after casing between 9 and 10 tube, accommodated in the engine room, and this caused considerable problems.

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HMS Triton

⚙ Triton class specifications
Displacement	1,090 tons surfaced, 1,326-1,575 tons submerged*
Dimensions	276 ft 6 in x 25 ft 6 in x 12 ft 9 in/14 ft 7 in (84.28 x 7.77 x 3.89 fwd/4.45 aft m*)
Propulsion	2 shafts diesel engines***, 1,250 hp (930 kW), 2 electric motors 1,450 hp (1,080 kW)
Speed	15.5 knots (28.7 km/h; 17.8 mph) surfaced, 9 knots (17 km/h; 10 mph) submerged
Range	131 tons**** fuel, Range 8,000 nmi (15,000 km; 9,200 mi)/10 kn surfaced
Armament	6 bow TTs, 4 external (16 torpedoes), QF 4 inch (100 mm) deck gun
Mex depth	250 ft (80m) normal, 300ft (96 m) max, 400+ ft crush.
Sensors	type 129, 138 sonars
Crew	48-59

*Triton 1,331/1,585t
**4347.4.58m for conways
***Default Vickers. Tigris, Torbay Admiralty diesels, Tribune, Tarpon, Tuna MAN diesels, Thunderbolt, Trident, Taku, Talisman Sulzer diesels.
****178t Trident, Torbay post refit.

General Overview

These fifteen pre-war submarines were ordered under the Programmes of 1935, 1936 (4), 1937 (7) and 1938 (3) and all had a bulbous bow covering the two forward external torpedo tubes which reduced surface speed in rough weather. They were removed from Triumph/Thetis during extensive repairs. Only six survived the war, less than half of the class. About the bow, Group Two boats had their external bow tubes moved further back making for a finer bow shape and causing speed loss. Their two of the external torpedo tubes were also reversed, facing aft, and there was an additional rear torpedo tube creating a characteristic hump. The final Group Three had their bows refined further with a new casing around the conning tower and the rear-facing torpedo tubes flattened for a much smoother profile. From there, the much larger A type were designed.

Jolly Rogers displayed by HMS Thunderbolt’s crew

Combat patrols were eventually done in the shallower Mediterranean, not the far east as planned. Triton was sunk in the Adriatic Sea on 18 December 1940, Thetis sank during trials in 1939 (all hands) and was salvaged, repaired, modified, recommissioned as Thunderbolt, in October 1940. She was Sunk by the Italian corvette Cicogna off Messina, 14 March 1942. Triumph was lost (probably Italian mines) on 14 January 1942, Tarpon (probably German minesweeper M-6) on 14 April 1940, Thistle was torpedoed by U-4 on 10 April 1940 off Norway, Tigris (probably sunk by German ship UJ-2210) on 27 February 1943, Triad by gunfire from Italian submarine Enrico Toti in the Gulf of Taranto, 15 October 1940, Talisman lost 17 September 1942 Mediterranean (probably Italian mines) and Tetrarch lost in Mediterranean (27 October 1941) due to Italian mines.
Tribune was one of six boats which survived the war. Built at Scotts in Greenock she was scrapped 1947, Trident in 1946, Taku in 1946, Truant was wrecked 1946 on way to breakers, Tuna was scrapped 1946 and Torbay in 1947.
Overall, they were liked for some points, like their greater torpedo firepower compared to any previous models, great range, but they were heavily critized for thiier poor seaworthiness in heavy weather, which made them barred from the Atlantic and relocated instead in the mediterranean.

Improvements: Group 2 and 3 boats

Group 2 boats

General outline of Group II boats
They were all ordered under the 1939 War Emergency Programme, Thrasher being launched on 5 November 1940. They underwent scores of modifications (see below).
The class comprised Tempest, Thorn, Traveller, Trooper, Turbulent (most successful sinking 90,000 tons of enemy shipping). They too had a lot of losses. The torpedo tubes were revised. The external ones were moved 7 feet aft to help with sea keeping. The two external forward-angled tubes close to the conning tower were repositioned aft, angled backwards to fire astern plus another stern external torpedo tube in chase. The forward volley was thus reduced to eight, three aft. Still 16 torpedoes in reserve, albeit changed for more gun ammo. They all had a cap to reduce drag on Group I, but this caused problems, and later the tubes had reshaped orifices, for minimal drag. Construction was revised also an introduced welding, whereas their CT shape was now standard with enclosed cabs (whuch was not appreciuated). All Group 2 soldiered like the Group 1 in the Mediterranean.
The adoption ofg an outer tube facing rearwards at the stern was tried on several Triton class, and this became standard on the Group 2 weheras amidships torpedo tubes were moved aft of the conning tower, also facing rearwards to allievet captain complaints and giving them more options. Initially angled at 10° off the centerline, this was later modified due to issue with made maintaining depth: HMS Traveller and Trooper and Group 3 boats had their angle reduced to 7°.

Group 3 boats

HMS Trenchant in 1944, author’s profile
This was by far the largest wartime group, with more than 31 boats. Welding was made mandatory for the whole construction after a lot of hesitation from July 1942, for the pressure hull only, then the entire hull in 1944. Being stronger and able to stay under 350 ft (107 m), they also carried more fuel in external ballast tanks and the early riveted external ballast tanks became welded as they were sent to the Far East. Indeed, oil leaks often betrayed their presence. The final estimated crush depth was estimated to 626 ft (191 m), which enabled to escape most ASW attacks. The same conclusion was reached for the late U-Boats, including the Type XXI.
Wartime austerity also urged production simplified, so they made without their jackstaffs and guardrails and a single anchor. Internal pipework was now in steel, not in copper. Fuel capacity ended at 230 long tons (230 t) for a 11,000 nmi (20,000 km; 13,000 mi) surfac range at 10 knots (19 km/h; 12 mph). But after the loss of HMS Tempest in 1942 (lead boat Group II) chnaged were made to the protection of the battieries. Indeed she had to surface in emergency after being depht-charged, being poisoned by chlorine gas from poorly protected battery cells combined with seawater leaks. She had to surrender. Instead of changing the batteries, it was decided for Group III boats to strengthen the battery compartment with rubber shock absorbers. HMS Terrapin survived a prolonged depth charge attack and kept her batteries working.
Nine were ordered under the 1940 Programme, P311 (lost before formally named Tutankhamen), trusty, Tactician, Tally Ho, Tantalus, Tantivy, Taurus, Templar, Trespasser, and truculent.
17 more were ordered under the 1941 Programme: Telemachus, Talent (Zwaardvisch), Terrapin, Thorough, Thule, Tudor, Tireless, Token, Tradewind, Trenchant, Tiptoe, Trump, Taciturn, Tapir (Zeehond), Tarn (Tijgerhaai), Talent, Teredo.
14 submarines were ordered under the 1942 Programm, five completed: Tabard, Totem (INS Dakar), Truncheon (INS Dolphin), Turpin (INS Leviathan), Thermopylae and nine ordered but cancelled on 29 October 1945, Thor (laid down at Portsmouth 5 April 1943, launched on 18 April 1944), Tiara (launched 18 April 1944), Theban, Talent, Threat and four unnamed, P345, P346, P347 and P348.

⚙ specifications Group II
Displacement	1,290 tons surfaced, 1,560 tons submerged
Dimensions	276 ft 6 in x 25 ft 6 in x 12 ft 9 in* (84.28 x 7.77 x 3.89 m)
Propulsion	2x diesels 1,250 hp (930 kW), 2x electric motors 1,450 hp (1,080 kW)
Speed	15.5 knots (28.7 km/h; 17.8 mph) surfaced, 9 knots (17 km/h; 10 mph) submerged
Range	131 tons fuel oil, 8,000 nmi (15,000 km; 9,200 mi) at 10 knots surfaced
Armament	6 bow TTs, 4 external (16 torpedoes), QF 4 inch (100 mm) deck gun
Sensors
Crew	48

*14 ft 7 in (4.45 m) aft

Wartime service

Prewar

HMS Triton as commissioned in 1939, one of the rare to have proper sea trials.
The lead boat Triton, was commissioned on 9 November 1938. Thetis was lost while on trials on 1 June 1939 and sank with 99 men on board. This trategy led to modifications in escape procedures. Triton was the only one to underwent full trials, as after september 1939 this was seen as a waste of time. Training commenced immedately and sea trials were combined with a shakedown cruise. In fact when the war started, the RN had only three T-class: HMS Triton, Triumph and Thistle. They were not sent to the far east but patrolled local waters the remainder of the year, before it was decided later in 1940 to send them to the Mediterranean as the most urgent.
They ended heavily engaged from the North Sea to the Mediterranean, only Far East for the rare survivors in 1944-45.

Wartime

HMS Tribune’s deck awash, color photo, AWM coll.
The British submarine campaign against Germany was very specific as no blockade was profitable, Germany being mostly autonomous and only dependent on Baltic and land routes (notably USSR prior to the summer of 1941). So the T class preyed on rare vessels spotted in the North Sea, heavily mined. These were long, dangerous and often fruitless patrols.
On 10 September 1939 Triton spotted another submarine, challenged her, got no answer and fired two torpedoes, sinking her. Unfortunately this was HMS Oxley, first British submarine lost in the war. Why she did not answered remained linked to the apparent lack of watchful eyse this night. In any case, just two crew surviving the attack. Triumph soon almost sank too, hitting a mine on 26 December 1939 but survived, repaired in Rosyth.
They had better luck from April 1940 whe the Norwegian campaign commenced, which brought opportunities: On 8 April 1940, Triton fired but missed Blücher and Lützow. 2 days later the sank three troopships. Truant hit also the cruiser Karlsruhe. But some were also lost nor long after, Thistle by U-4 on 10 April, Tarpon by Q-ship Schiff 40/Schürbek on 14 April.
Next, T class established patrols in the strategic Bay of Biscay (the ‘Iron Ring’) from July 1940 as the battleof britain took place. Occupation of French Atlantic ports now allowed valuable kriegsmarine assets to be based on the coast in 1941.

HMS Seadog (foreground) and Thunderbolt in Holy Loch, Scotland.

Then the Mediterranean started from September: On 15 December 1940, Thunderbolt torpedoed Capitano Tarantini, one of the 14 Axis submarines sunk by T-class collectively. On 5 July 1941, Tigris sank Michele Bianchi. Triton class also patrolled during the infamous ‘Channel Dash’, February 1942. Triton class targeted the the Italian Regia Marina, which trained a lot in ASW warfare and had a good sonar the ecogoniometro (ECG) mounted in many escort vessels, including the excellent Gabbiano, small VAS and many others. Mines was used as an art form where it matters and took a fair shere of T class subs as well. In fact the Italians gained an ASW tally comparatively higher than Germany or Japan and it shows in the losses of all British types.
In addions waters were mostly calm, shallow, and clear waters so that aviation could spot them with ease from the air, even well submerged, whereras shallow waters made ineffective the deep diving abilities of the large T class. But they enjoyed far greater endurance on this theater compared to the smaller S, V, U types. They operated from Alexandria and Gibraltar and could cross mid-way through the central Mediterranean and back with ease.

Design to sink warhips, the Triton class spent much time hunting down Axis convoys to North Africa and only when Malta had enough aviation to chase off axis patrollers and do reconnaissance and attacks, rhis “blind spot” was covered by British submarines. As aviation was always a danger, they stayed surfaced to recharge only at night and sailed at persicope depht most of the time, at slow speed. 13 T-class were lost in this theater, 50% to mines. But they did well like Turbulent sinking over 90,000 tons of Axis shipping. J. W. Linton of Turbulent was awarded one of the four Victoria Crosses (VCs) for all classed, and for Mediterranean campaign. Thrasher and Torbay (for a daring raid into Corfu) as well.

Of the Triton class, only Truant and Trusty were ordered to Singapore but were underway when it fall adn they ended based in Ceylon with the surviving Dutch submarines for an Indian Ocean campaign against IJN communications lines in the east indies. They also were on faction during the Indian Ocean Raid. Truant sank two IJA transports. By late 1943 the situation changed, but successes awaited still Group II boats. There were few targets of opportunity in the area, but the all Group III and most Group II surviving were found more adapted to far Eastern operations.

Note: There will be upgrades in this wide subject in the future, with more data on Group II-III, modernizations and postwar upgrades, exports, career of individual boats of the 1940 war emergency and 1941-42 programmes.

Career of The T class

HMS triton was laid down on 28 August 1936 at Vickers Armstrong, Barrow-in-Furness, launched on 5 October 1937, commissioned on 9 November 1938. Assigned to the 2nd Submarine Flotilla by late August 1939, she was deployed at Dundee and Blyth. The day the war started she was on patrol on the Obrestad line, off Norway, on 24 August 1939. On 19:55 on 10 September Triton was surfaced off the Obrestad Light in a slow zigzag patrol while charging batteries. Lt. Cdr Steel leeft the post after placed lookouts on the bridge with the officer of the watch. At 20:45, he was called to the bridge when was spotted something, and orcered torpedo tubes 7 and 8 prepared for firing, until a submarine was recoignised low in the water.
The signalman sent three challenges and waited several minutes, go no answers. Captain Steel wondered if this could be HMS Oxley, off her next assigned patrolling area. No study of the silhouette, could give up the type. Then three green rifle-grenade flares were fired and 15 second s were waited still without answer, thus Steel believed he had an U-Boat facing him and ordered to place the boat for a volley, firing tube 7 and three sec. later tube 8. An explosion was heard and he ordered full speed ahread to see the wreck and confirm the kill. However the Aldis lamp only revealed three men amid oil and debris, duly brought on board and interrogated, with quite a surprise. These were Oxley’s men on watch on the bridge, Lt. Commander H.G. Bowerman (CO) Able Seaman Gluckes, lookout but Lt. F.K. Manley disappeared. The Board of Enquiry concluded this was ot Steel’s fault as he was reasonable in his attempts. Not only Oxley was out of position and bizarrely it seems none on the men on watch saw tTriton’s signals. This forst T class success was however still a “friendly fire.” camouflaged as an accidental explosion to keep morale and postwar, this was changed to a collision with Triton, and only revealed in the 1950s.
Next Triton patrolled the Baltic waters and near the Skagerrak, she caught on 8 April the cruisers Blücher, Lützow and Emden off Skagen, fired ten and missed. On 10 April 1940, she sank the steamers Friedenau, Wigbert, andpatrol vessel Rau 6, all in the Kattegat.
Next her Mediterranean campaign commenced, based from Alexandria. While in the Gulf of Genoa, Lieutenant Watkins tried to enter Savona, spotted and claimed a supply ship at anchor (8,000-ton, unconfirmed). As no other vessel was worth a torpedo, her surfaced and started shelling a large factory and gas works before departing. He notably damaged the Cieli Electric Station.
On 28 November 1940, Triton left Malta for the southern Adriatic and on 6 December, the admirakty was informed of the sinking of the merchant Olimpia attributed to Triton bnut the latter never went back to comunication and was not heard. It is now presumed lost on 18 December and Olimpia survived being towed to port whereas the Regia Marina Triton sunk by the torpedo boats Confienza or Clio, the British stating mines in the Strait of Otranto instead.

HMS Thetis was built at Cammell Laird in Birkenhead, launched on 29 June 1938 and after completion her forward hydroplanes jammed. Her trials were completed in Liverpool Bay under Lt. Commander Guy Bolus and diving trials with the tug Grebe Cock. She carried 59 men and Yard’s technical observers for 103 total. First dive was attempted at 14:00 on 1 June 1939 but she too light and checks were made, notably flooding the tubes, done by Lt. Frederick Woods (torpedo officer), which opened the test cocks. But those on tube 5 were blocked by enamel paint. Plus there was confusing in the layout of the bow cap indicators, arra,ged vertically placing 5 at the bottom while its “Shut” position on the dial mirrored tube 6 above. Long story short, the the inner door of the tube was opened and water rushed inside so violently there was no time to close the compartment. The whole submarine hit the seabed 150 ft (46 m). Woods, amazingly, survived to tell the tale and maintained his version all his life (all indicators “Shut”). At least an indicator buoy was released with its smoke candle fired indicated to the tug at 16:00 that something went wrong, contacting HMS Dolphin at Gosport. The rescue started. Her stern remained surfaced, with Frederick Woods, Captain Harry Oram and Leading Stoker Walter Arnold and Cammell Laird Fitter Frank Shaw escaping in time. The others were overcome by carbon dioxide poisoning, massive atmospheric pressure and 20 hours before the evacuation started. 99 were lost, including 26 Cammell Laird workers, 15 officers, Vickers-Armstrong employees, caterers and the Mersey pilot. She was spotted late by the destroyer Brazen.
The survivors used the 4-men large aft escape chamber but other escapees drawned.
The Admiralty successfully blocked the disclosure of the contract and it was accepted by judges. The case draw the urge for better ergonomics.
The Liverpool & Glasgow Salvage Association was commissioned for the salvage during which a diver died from “the bends” on 23 August 1939. On 3 September, just towed, Thetis was grounded ashore at Traeth Bychan in Anglesey and bodies were extracted for the naval funeral, with full honours.
An HMS Thetis memorial was later erected at Woodside in Birkenhead and another to Maeshyfryd Cemetery in Holyhead in 1947. After being repaired to avoid the bad luck associated with such event, she was renamed HMS Thunderbolt, under the command of Lt. Cdr. Cecil Crouch. She was rushed into service and spent 18 months in the Atlantic, Bay of Biscay in which she spotted and sank on 15 December 1940 the Italian submarine Capitano Tarantini, en route to the recently axis submarine base of Bordeaux (BETASOM).
Later in 1942, Thunderbolt and Trooper, P311 was modified to carry two “Chariots” and crews to target Axis shipping in harbour, transferred by December 1942.
She took part in Operation Principal by December 1942, Thunderbolt being assigned Cagliari, but this was not a success. P311 was lost at La Maddalena.
Next she was assigned to Palermo harbour in January 1943, and more successful and on 2–3 January, mined sank the incomplete light cruiser Ulpio Traiano and freighter SS Viminale.
Next raid was in Tripoli harbour on 18 January, to hit any prepared blockships priot to the occupation by the 8th Army.
On 20 February 1943 she shelled the Albanian sailboat Villanzen Veli off Bari but was chased off by the auxiliary cruiser Brindisi and a coastal battery.
She was sunk on 14 March 1943 off Sicily, hunter down by the Gabbiano class corvette Cicogna after being detected her depth charged under 1,350 m (4,430 ft) withh all hands.

Tribune, built at Scotts, Greenock, commissioned 17 October 1939, was part of the 1st group, T class submarines and she started the war with North Sea operations, attacking an unidentified German submarine later revealed as U-56, German tanker Karibisches Meer, German merchant Birkenfels but missed all. Mediterranean: She hit and damaged the French merchant Dalny, beached and gunned. She damaged the German tanker Präsident Herrenschmidt, Italian merchant Benevento, missed.
She was taken as base for the 1943 British wartime propaganda film “Close Quarters” impersonating “HMS Tyrant” in the North Sea. She survived the war and sold for scrap in July 1947 (Thos. W. Ward in Milford Haven).

Trident built at Cammell Laird, commissioned 1st October 1939, and in May 1940, she operated in Kors fjord Norway, spotting and sinking a German supply ship. From 1941 to mid 1943 she stayed in the North Sea, sinking the German merchants Edmund Hugo Stinnes 4, Ostpreußen, Donau II, Hödur and Bahia Laura, the tanker Stedingen and auxiliary submarine chaser UJ 1213. She attacked, damaged the Cläre Hugo Stinnes and Levante, missed the Palime, Wandsbek, Pelikan and Altkirch, oiler Dithmarschen, hospital ship Birka, minesweeper depot ship MRS 3 (better known as Bali) and U-31. From her Polyary based in Russia, she spotted but missed U-566. She also spotted, engaged, but mostly missed the Prinz Eugen and Admiral Scheer on 23 February 1942. Prinz Eugen was hit in the stern but she survived. Her unusual mascot was a… young reindeer presented as gift by the Russians in August 1941, named “Pollyanna” which once ate a few navigations maps. She ended in a local zoo, still reacting to the sound of whistle.
In the Mediterranean, Trident sank five sailing vessels, damaged the Italian merchant Vesta, German GA 41, attacked the auxiliary UJ 2202. She missed the Italian merchant Agnani and French passenger/cargo ship Cap Corse. She was reassigned to the far east and arrived in Colombo by mid 1943. She sank a Japanese sailing vessel, a Daihatsu landing craft (bu gunfire off Batu islands, Indonesia) but missed the cruiser Kashii. Back home she was sold for scrap on 17 February 1946, BU in Cashmore, Newport.

Triumph built by Vickers, Barrow-in-Furness, launched 1938, and commissioned by May 1939. She operated from Dundee and Blyth, and on 26 December 1939, hit a German mine, loosing a 18 feet (5.5 m) section of her bow and had her pressure hull damaged, but torpedoes did not detonate. She was repaired at Chatham until 27 September 1940 and was sent to the Mediterranean in early 1941, sinking the Italian merchants Marzamemi, Colomba Lofaro, Ninfea, Monrosa, auxiliary patrol vessels V 136, Valoroso, V 190, V 137, the tug Dante de Lutti, salvage vessel Hercules, German merchant Luvsee, Greek sailing vessels Panagiotis and Aghia Paraskevi, damaged the Italian armed merchant cruiser Ramb III, tankers Ardor and Poseidone, merchant Sidamo, German merchant Norburg and satrted to be used for covert operations. She was tasked to carry commandos for Operation Colossus, cancelled. By December 30, 1941 she landed agents at Antiparos in Greece but failed to pick up agents on 9 being lost by a mine, sinking with all hands, adn her wreck was rediscovered in June 2023 by Kostas Thoktaridis under 203 metres, confirming the mine.

Taku was laid down on 18 November 1937, launched 18 May 1938, commissioned 3 October 1940. In April 1940 she fired on HMS Ashanti bu mistake but missed. In May she attacked a German convoy, damaged the torpedo boat Möwe, and by November, missed the tanker Gedania. In the Mediterranean by 1941, she sank the Italian merchantmen Cagliari, Silvio Scaroni, passenger/cargo ship Caldea, German munitions transport Tilly L. M. Russ, Italian auxiliary minesweeper Vincenso P., Italian tankers Arca and Delfin, Greek sailing vessels Niki, Lora and another. She missed the German merchant ship Menes, Italian tanker Cerere. She was repatriated to the Scandinavian coast in 1944, sank the German merchantmens Rheinhausen, Hans Bornhofen, badly damaged Harm Fritzen. In March she missed the Kriegsmarine transport Moshill. She hit a mine in April 1944, badly damaged, but limped to port and was not repaired. She was sold in November 1946, BU in South Wales.

Tarpon was laid down on 5 October 1937, launched on 17 October 1939 and Commissioned on 8 March 1940 and had a short career in the North Sea. She left Portsmouth on 5 April 1940 for Rosyth with HMS Severn and sailed for Norway. The 10th she was assigned her first patrol route, but could not be reached again. By combining British and German records it seems she as detected and engaged by Schiff 40, a Q-ship also known as Schürbek, attacked her but missed and the latter reteliated with depth charges. The action was decribed by the Germans taking place in the morning and a second pattern brought wreckage to the surface, she stayed ald left at 05:00 the next morning. In Britain, Tarpon was reported overdue on 22 April 1940. The wreck was found and identified near Thyborøn by Danish commercial diver Gert Normann Andersen from JD-Contractor with British marine archaeologist Dr Innes McCartney, in March 2016 under 40m of water. There was a live TV program about her on 28 August 2016. Her two torpedo tubes were empty and damage confirmed depth charges.

Thistle was Laid down on 7 December 1937, Launched on 25 October 1938, Commissioned on 4 July 1939. She was part of the 2nd Submarine Flotilla and on 26-29 August 1939 deployed from Dundee and Blyth under Lt. Wilfrid Frederick Haselfoot. Her first patrol patrol off Stavanger was motiovated by intel about the invasion of Norway being imminent. On 10 April she sailed there after her previous patrol, wirh two torpedoes remaining after missing an U-boat. She was then ordered off Skudenes and no contact was made again.
It seemed that U-4 (a small Type IIa), that she previously attacked, sighted her surfaced by night and torpedoed her as confirmed by her logs postwar. Thistle attack happened at 16:04 hours on 9 April 1940, firing six torpedoes and missing, as reported via radio.
U-4 spotted the wakes and evaded by crash diving, and evolved, surfaced, search for her attacker ahnd found her later surfaced, charging batteries. She took position at 02:13 hours on 10 April and fired two torpedoes, a G7a which missed and a recent magnetic G7e which hit. it happened off Skudenes. Her wreck was rediscovered by the Norwegian Institute of Marine Research, spring 2023 under 160 meters and conformed in October 2023.

Tigris was Laid down on 11 May 1938, launched on 31 October 1939 and Commissioned on 20 June 1940. She operated in the Bay of Biscay from July 1940, under Howard Bone, sank the French fishing vessels Sancte Michael, Cimcour, Charles Edmond and Rene Camaleyre, merchantmen Jacobsen and Guilvinec, German tanker Thorn and attacked but missed among others U-58 On 5 October 1940, as well as two Italian submarines from Bordeaux, Reginaldo Giuliani and Maggiore Baracca.
On 5 July 1941 she sank Michele Bianchi 150 nm off the Gironde estuary and was reassigned to the north sea by mid-1941. Off Finnmark, she sank the Norwegian Haakon Jarl and Richard With. Next, reassigned to the Mediterranean, from late 1942, on 6 December, she sank the Italian submarine Porfido, with commander George Colvin, later awarded the DSO. On 21 January 1943, she sank the Italian merchant Citta di Genova, in the Strait of Otranto.
She left Malta on 18 February 1943 for Naples and on 22 February attacked the merchant Teramo, presumably as she was never head of again. She was last sighted at 0730, 24 February, 39 miles from Capri. She was claimed by the German submarine chaser UJ 2210 (Otto Pollmann), escorting a convoy off Capri, having a contact and making three depth charge attacks, a third bringing oil to the surface, and anothr attack creating a huge air bubble. Tigris was overdue to Algiers on 10 March 1943 and is believed sunk on 27 February.

HMS Triad was laid down on 24 March 1938, launched on 5 May 1939 and commissioned on 16 September 1939. She patrolled the north sea at the start of the war, and by April 1940 while off Norway, she sank the German troop transport Ionia and missed the German depot ship Tsingtau.
She was redeployed in the Mediterranean and on 9 October 1940 departed from Malta to the Gulf of Taranto, then bound to Alexandria but was overdue there by 20 October. Now it was establmished she was torpedoed and sunk with all hands on the night of 14/15 October by the Italian submersible Enrico Toti which was instead being attributed HMS Rainbow. At the time it happened she was under command og Lt.Cdr. G.S. Salt.
As reconstructed from postwar Italian logs it happened at 01:00 on 15 October 1940, when Enrico Toti sighted a large submarine about 1,000 metres (3,300 ft) port of her, and it seemd Triad spotted her also both starting a deadly dance to be in torpedo position. It was claimed the British opened fire first (gunfire) but missed and a torpedo which Enrico Toti avoided, then closed at top speed, and started to fire, by Gun and MG-fired, compelling the British crew to leave the deck and run for cover. As triad started to dive, Enrico Toti fired a single torpedo which hit her, after lainding already two 120 mm hits. This happened south-west of Calabria in about 30 minutes, and later narrated by Famous Italian writer Dino Buzzati which made interviews of the crew and became a celebtriy for his report live at the Battle of Cape Matapan. The story was published in October 1940. Confusion with Rainbow was cleared by historians in 1988, crossing data and logs, but her wreck was not found.

HMS Truant was laid down on 24 March 1938, launched on 5 May 1939 and commissioned on 31 October 1939. In March 1940 off Norway she damaged KMS Karlsruhe off Kristians and, and she was latter scuttled by the TB Greif. Truant later attacked the British merchant Alster but missed. She intercepted the German merchant Tropic Sea in the Bay of Biscay, recaptured 8,000 tons of wheat and the POW captain and 22 survivors of SS Haxby sunk earlier by the raider and the Norwegian crew. Truant wa smistook and torpedoed, missed, by the River-class submarine Clyde.
She was sent to the Mediterranean in May 1940, and sank many ships, such as the Italian merchant vessels Providenza, Sebastiano Bianchi and Multedo, tankers Bonzo and Meteor, auxiliary submarine chaser Vanna, passenger/cargo ship Bengasi, German merchantman Virginia S. and damaged the tanker Prometeo, torpedo boat Alcione (later total loss) but missed the merchants Utilitas, Silvia Tripcovich, Bainsizza and Arborea, tanker Labor, German merchantman Bellona.
She was then reassigned in early 1942 for the Far East, taking part in the Battle of Badung Strait, spotting the Japanese covering force, missed the cruiser Nagara, sunk the merchants Yae Maru and Shunsei Maru in the Malacca Strait, missed a large liner (hospital markings, possible Hikawa Maru) and destroyed by gunfire the Japanese army cargo ship Tamon Maru No.1 on her final patrol in late 1942 engine trouble.
Back to home waters for repairs and refits from December 1942 until May 1943, she was used for training and made a patrol to find Tirpitz but was soon ordered back to the Far East, marred by repairs after engine troubles. She stayed in local waters as trials ship for 1945, sold on 19 December 1945 but wrecked in December 1946 en route to the shipbreakers.

HMS Tuna was laid down on 13 June 1938, launched on 10 May 1940 and commissioned on 1 August 1940. Tuna sank the 7,230-ton merchantman Tirranna, on 22 September 1940 (captured by the German armed merchant cruiser Atlantis in the Indian Ocean), 87 went with her. She later sank the German catapult ship Ostmark and French tug Chassiron, but also the German submarine U-644 and missed U-302 and Italian submarine Brin as well as the German tanker Benno (also Atlantis capture).
In January 1941 with her sister HMS Snapper they captured and took as prize the French minesweeper La Capricieuse to Bishop Rock but Snapper left, later presumed lost. Tuna chased on U-boatfor an hour, fired her deck gun and damaged her conning tower, the latter returned fire, no damage. She withdrawn as reinforcements arrived. By February 1942 she sailed to Trondheim with HMS Trident, protecting a troop convoy. On 30 November 1942, under Lt-Cdr Dick Raikes (DSO,) she left Holy Loch in Scotland for a covert operation with 12 Royal Marines swimmer canoeist commandos sneaked into Gironde estuary (Operation Frankton, attack on Bordeaux harbour) but was delayed by bad weather and a minefield and surfaced a day late 10 miles (16 km) from the mouth. During the canoe launch was was damaged, but the remainder went on and paddled 60 miles up the Gironde into Bordeaux. This was was a success which costed dearly, only Corporal Bill Sparks and Major Herbert Hasler surviving. Thi s experiment led to the formation of the Special Boat Service. The story led to the film the “Cockleshell Heroes”.
She performed four more war patrols on 18 November 1943 and sank no less than three U-boats making Lt. D. S. R. Martin, a recipient of the DSO with two bars with others awarded to Lt (E) N. Travers, Chief Petty Officer William J Stabb and Leading Seaman Dominic “Bommy” King.
No logs for the remainder of her service. In August 1945, she attended to enter Rotterdam in advance of the cruiser HMS Bellona and destroyers Garth and Onslow and the Free Dutch T-class Dolfijn and Zeehond. She sold for BU 19 December 1945.

HMS Talisman was laid down on 27 September 1938, launched on 29 January 1940 and commissioned on 29 June 1940. Early in her service she captured the French fishing vessel Le Clipper. In British service she was used to observe U-boat movements off the Gironde estuar and ended later in Falmouth. She later torpedo-missed HMS Otus, mistaken. She sank two sailing vessels and the Vichy-French liner Théophile Gautier and Italian merchant Calitea, German merchant Yalov, damaged the merchant Salzburg, missed the Italian merchant Lauretta, heavily depth charged by the TB Libra. She left Gibraltar on 10 September 1942f for her last mission, carrying supplies to Malta, due on 18 September. She reported a U-boat off Philippeville in Algeria on 15 September underway, where was sent a Sunderland of 202 Sqn, which caught and sank the Italian submarine Alabastro. Talisman is presumed sunk by an Italian mine off Sicily of by surface forces on 17 September, her wreck was never found.

Tetrarch was laid down on 24 August 1938, launched on 14 November 1939 and commissioned on 15 February 1940 and the only T class ever completed with a minelaying equipment. In Home waters, first success was in May 1940 when sank the the sub-chaser UJ B in the Skagerrak. She sank the Danish fishing vessel Terieven, German tanker Samland, captured the Danish trawler Emmanuel and was reassigned to the Mediterranean in late 1940. She sank the Italian merchants Snia Amba, Giovinezza and Citta di Bastia, tanker Persiano, sailing vessels V 72, V 113 and Nicita, Greek sailing vessel Panagiotis Kramottos, damaged the German merchant Yalova and missed the Greek tanker Olympos.
She sailed to Malta on 26 October 1941 and departed for a refit back home bound for Gibraltar. but failed to arrive on 2 November, overdue, likely lost to a minefield. She still communicated on Monday 27, presumed sunk off Capo Granditola in Sicily by late October 1941. Wreck never found.

HMS Torbay was built at Chatham, laid down on 21 November 1938, launched on 9 April 1940 and commissioned on 14 January 1941. By March 1941 she left Portsmouth on her first patrol, trying to ambush Scharnhorst and Gneisenau heading for Brest after their sortie in the North Atlantic. She missed them and was ordered to Gibraltar, then 1st Flotilla at Alexandria.
For 12 months, she sank many ships and the Italian submarine Jantina as well as taking part of special operations.
Probably the best known was around Crete: Her mission was to surface bby night and evacuate Allied stragglers still roaming free after Crete surrendered to the Germans on 1 June. On 22 August 1941, she was found carrying 130 British and Anzacs to Alexandria, making a record. Commander Anthony ‘Crap’ Miers (VC) made it a ritual to salute Vichy French sailors aboard French ships at anchor in Alexandria every time he entered the port, with the crew assembled on deck, dropping trousers, ‘mooning’ them.
In July 1941 she was accuded twice of alleged war crimes, firing on axis troops swimming in the water, as written in the logs. He was strongly word reprimanded, but kept attacking Axis convoys, on 10 June 1941 off the Dardanelles, making a hit on the Italian tanker Utilitas (dud) and hit on tanker Giuseppina Ghirardi (sank), then on 12 August 1941 west of Benghazi on the Bosforo and Iseo (missed) and heavily depth charged..
By November 1941 he was tasked with landing commandos (Geoffrey Keyes) in Operation Flipper, not a success. On 15 December 1941 he sank the ex-Italian German merchant Sebastiano Veniero off Methoni (Peloponnese), after being already hit by HMS Porpoise.
On 4 March 1942 in Corfu he spotted a destroyer and two 5,000 ton transports, hit the latter presumed sank but escape a heavy depth charge attack. Anthony Miers ws awarded the VC for his 17th patrol in the area. Back to Britain for a refit, HMS Torbay was in the Mediterranean by February 1943 under Lt. Cdr. Robert Clutterbuck for more successful patrols, and nearly sunk by the Q-ship GA 45 by October 1943, periscope sighted, depth charged. A night deck gun atack failed as she was spotted and fired at back. Fortunately GA 45 run out of DCs. Next in early 1945 she was ordered to the Pacific Far East, arriving in May 1945 under Lt. C.P. Norman, sinking notably two Japanese sailing vessels, a coaster, damaged another.
She was sold for BU on 19 December 1945, scrapped March 1947.

Read More/Src

Books

Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Periscope Publishing.
Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis, Maryland: Naval Institute Press.
Brown, D. K. (2000). Nelson to Vanguard. Chatham Publishing.
Clayton, Tim (2011). Sea Wolves. London. Abacus.
Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). Chatham Publishing.
Chesneau, Roger, ed. (1980). Conway’s All the World’s Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press.
Greentree, David (2016). British submarine vs Italian torpedo boat : Mediterranean 1940-43. Oxford: Osprey Publishing.
Kemp, Paul J. (1990). The T-class Submarine: The Classic British Design. Annapolis, Maryland: Naval Institute Press.
Mars, Alistair (1971). British Submarines at War 1939-1945. London. William Kimber.
McCartney, Innes (2006). British Submarines 1939–1945. New Vanguard. Vol. 129. Oxford, UK: Osprey.
van den Pol, E. (1989). “Aspects of submarines – Part I: Some notes on development”. Schip en Werf. Vol. 56, no. 10. Rotterdam: Wyt & Zonen. pp. 352–358.

Links

uboat.net/
transportsofdelight.smugmug.com
battleships-cruisers.co.uk/triton_class.htm
worldnavalships.com/triton_class.htm
navypedia.org/ t_prewar.htm
navypedia.org t_war_1940.htm
navypedia.org/ t_1941_1942
en.wikipedia.org British_T-class
navweaps.com British Torpedoes
rmg.co.uk/collections/
commons.wikimedia.org/ British_T_class_sub
rnsubs.co.uk/ sonar.html
uboat.net: Triton
rmg.co.uk/collections/
laststandonzombieisland.com/
hansonclan.co.uk/
britsub.x10.mx/ t_class3_1940.html
deviantart.com/ British-T-Class-Submarine
dailypost.co.uk/ hms-thetis-sank-coast
dailyecho.co.uk/
thefreelibrary.com/
uboat.net/

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