Jack Sargent was born on 19 May 1914, the son of Harry Bertram Sargent (a commercial traveller) and Margaret Sargent. When the 1939 Register was compiled in September 1939 Jack Sergeant was listed as a clerk and traveller, at home with his parents and younger brother, Harry, at 23, Banklands Lane, St Albans, Hertfordshire.

He joined the Royal Navy Volunteer Reserve and was appointed Temporary Sub Lieutenant on 16 October 1941. In June 1942 he was listed as serving in HMS DOLPHIN. He was promoted to Temporary Lieutenant RNVR on 16 October 1942. A volunteer for ‘Special Service’ Jack Sargent trained as a Charioteer at HMS VARBEL. During his training as a Chariot No. 1 Crewman he was teamed up with Ordinary Seaman Robert Anderson as his No. 2 Crewman. When carrying out a training ‘night attack’ on the battleship HMS HOWE, Robert Anderson accidentally snagged and punctured his diving suit – which flooded up. This caused a problem as the attack progressed and Jack Sargeant decided to abandon the attack and return to base.

Jack Sargent was allocated to a team of charioteers formed for an operation to attack Italian shipping at the port of La Maddelena. The team was embarked in HMS P311 for the operation with three chariots – Nos. X, XVIII & one other. P311 had completed the passage through the Sicilian Channel – reported at 0130 on 31 December 1942 – but no further reports were received from the submarine and P311 was presumed lost with all hands in a minefield near La Maddelena on or about 2 January 1943. Also lost were the three chariots, the three chariot crews and the team of four dressers – ten personnel in all. The date of the loss of P311, her crew and her chariot passengers was assumed to have been 8 January 1943 which is the date that the submarine was due to arrive back at Malta.

Jack Sargent is commemorated on the Portsmouth Naval Memorial on Panel 80 Column 1 and on the 12th Submarine Flotilla memorials at Rothesay on the Isle of Bute and at Kylesku.