- Class: U class, second group - 12 submarines of 1939
- Displacement: 540 tons surfaced; 730 tons submerged
- Dimensions: 191.5 x 16 x 12.75 ft.
- Machinery: 2-shaft , Paxman Ricardo diesels plus electric motors, 615hp/825hp = 11/9 knots
- Armament: 1-3 in. gun; 6-21 in. T.T. (4 bow internal, 2 bow external + 4 reloads)
- Complement: 31
- Builder: Vickers-Armstrong, Barrow-in-Furness
- Laid Down: 30 Oct 1939
- Launched: 8 Jul 1940
- Completed: 31 Oct 1940
- Notes: The most successful British submarine of World War II, she was commanded for her entire career by LtCdr David Wanklyn, VC. Stationed at Malta from Dec 1940, she completed 24 war patrols, sinking 128,000 tons of shipping, including three large transports: the 18,000t SS Conte Rosso on 25 May 1941 and the 19,000t MS Neptunia and 19,000t MS Oceania on 18 Sep 1941. She also damaged the Italian cruiser Giuseppe Garibaldi on 28 Jul 1941, putting the latter out of action for several months. Other successes include sinking the Italian destroyer Libeccio on 9 Nov 1941, the Italian submarines Ammiraglio Saint Bon on 5 Jan 1942 and Tricheco on 18 Mar 1942, and ten cargo ships, two tankers, and a trawler. Lost on her 25th patrol off Tripoli obout 14 Apr 1942.