HMS GRAMPUS (Lt Cdr C A Rowe) sailed from Malta on 10 June 1940 for a patrol off Augusta. She was due to lay mines off the port and, on 13 June, reported that she had done so. She was due to return to Malta on 25 June but failed to arrive. It was assumed at that point she was lost with All Hands.
Following claims by Axis forces that an unknown submarine had been sunk in the central Mediterranean in mid-June 1940, it is now believed that Grampus was detected on 16 June by Italian anti-submarine vessels, attacked and sunk with All Hands.