HMS REGENT (Lt W N R Knox) sailed on 11 April 1943 from Malta to patrol in an area off the south coast of Italy. A submarine thought to be REGENT was sighted off Calabria on 13, 15 and 16 April. On 18 April she fired a torpedo at a merchant ship off the port of Monopoli but missed astern and the torpedo exploded on the shore. Later that day, a large explosion at sea was heard in Monopoli which is thought to have been REGENT striking a mine. She was listed as lost on 1 May 1943.

The entire crew of sixty-three Officers and Ratings were lost. The first of four bodies (none were identified) was washed up near Brindisi on 1 May 1943. This was the body of an ERA dressed in overalls and wearing a DSEA escape kit. Another body was washed up at Santa Andrea di Missipezza on 15 May 1943 also wearing a DSEA kit. On 16 May a body (of either an Officer or a Petty Officer) was washed up at Torre Santo Stefano, north of Otranto and, on the same day, another body was washed up at Castro Marina.