HMS H42

HMS H42 was a British H class submarine built by Armstrong Whitworth, Newcastle Upon Tyne. She was laid down in September 1917 and was commissioned on 1 May 1919.

On 23 March 1922, H42 was practising torpedo attacks against British destroyers steaming off Europa Point, Gibraltar, when she surfaced unexpectedly only 30 or 120 yards (27 or 110 metres) – sources differ – ahead of the destroyer HMS Versatile (D32). Versatile, making 20 knots, went to full speed astern on her engines and put her helm over hard to port, but had not yet begun to answer her helm when she rammed H42 abaft the conning tower, almost slicing the submarine in half. H42 sank with the loss of all hands. An investigation found H42 at fault for surfacing where she did against instructions.