Although built for service in the First World War, the only H21 Class submarines to be lost on active service were, ironically, during the Second World War - over 20 years later. The H49 was depth charged off the Dutch coast in October 1940 and the Barrow-built H31 was lost, presumed mined, in the Bay of Biscay on Christmas Eve 1941.
The last H21 Class submarine to be taken out of service was the H34 - in October 1945 - 28 years after she was laid down at Cammell Laird.
1917-1934
R Class submarines, the forerunners of the modern-day hunter-killers, were built on the premise that a submarine with an exceptionally high submerged speed and with the ability to launch a number of torpedoes might be able to overtake and sink the enemy.
