March 18, 1904 One of the first operational submarines of the Royal Navy was lost due to an accident. The
HMS A-1 was conducting a training attack off Portsmouth when she was run down by the SS Berwick Castle. In the exercise the A-1 was to attack the HMS Juno, which was sighted heading to Portsmouth but, when A-1 began to move in the Berwick Castle, unaware of the operation, hit the sub near the conning tower and sent her to the bottom.

The captain of the Berwick Castle believed he had been hit by a practice torpedo so no search was made for A-1. Only when A-1 did not return was a search made for her. None of the 11 man crew survived the sinking. The
A-1 was later raised and used as a target.