HMS L55 (Lt Cdr CMS Chapman) was deployed to the Baltic in 1919 during the Russian Intervention .
During operations against the Russian Fleet on 4 June 1919, L55 was sunk in action with destroyers Gavril and Azard (near Kronstadt in the Gulf of Finland). L55 fired two torpedoes at the destroyers which missed; then the submarine inadvertently surfaced and was hit by shellfire from the Russian warships. The pressure hull was not penetrated but the L55 then struck a mine on the edge of a British laid minefield and was lost with all hands. L55 was reported missing on 9 June 1919.
In 1928, the wreck of L55 was recovered; the bodies of 34 crew members were returned to England aboard MV Truro and buried in a mass grave in Haslar Royal Naval Cemetery.
The submarine was refitted and incorporated into the Russian Fleet as a training submarine, and formed the basis of the Russian L Class mine-laying submarines.