- Class: T class, first group - 15 submarines of 1936-38
- Displacement: 1,090 tons surfaced; 1,575 tons submerged
- Dimensions: 273 x 26.5 x 16 ft.
- Machinery: 2-shaft , Vickers diesels / Laurence Scott electric motors, 2,500hp/1,450hp = 15/9 knots
- Armament: 1-4in, 1-20mm A.A. guns; 11-21in T.T. (6 bow internal, 2 bow external, 2 admidships external pointing forward, 1 aft external + 6 reloads)
- Complement: 61
- Builder: Cammell Laird & Co Ltd, Birkenhead
- Laid Down: 21 Dec 1936
- Launched: 29 Jun 1938
- Completed: 26 Oct 1940
- Notes: Launched as HMS Thetis, she sank during sea trials on 1 Jun 1939 with the loss of 99 out of 103 men on board, including many other naval personnel and civilian constructors. Salvaged, repaired and commissioned as HMS Thunderbolt. Served in the Atlantic for 18 months from commissioning. Sank the Italian submarine Tarantini 15 Dec 1940 in the Bay of Biscay. Converted to carry two 'Chariot' manned torpedoes in autumn 1942 and sent to the Mediterranean, where her charges mined two ships at Palermo the night of 2-3 Jan 1943. Sunk with all hands by the Italian corvette Cicogna off Cap St Vito 14 Mar 1943.