Post-H20 British H-class submarines had ranges of 2,985 nautical miles (5,528 km; 3,435 mi) at speeds of 7.5 knots (13.9 km/h; 8.6 mph) when surfaced.

[2] H49 was laid down at William Beardmore and Company's Dalmuir shipyard on 21 January 1918, was launched on 15 July 1919 and completed on 25 October 1919.

Following the fall of France in June 1940, these training submarines undertook operational patrols in the North Sea as an anti-invasion precaution.

[10] On the afternoon of 18 October, under the command of Lieutenant R E Coltart DSC,[10] H49 was on her "billet" (prescribed patrol area) off the Dutch coast, when the unusual decision was taken to surface in daylight, probably presuming that the poor visibility would prevent their being sighted.

[11] Despite diving at once, H49 was sunk by depth charges from the German patrol craft UJ111, UJ116 and UJ118, commanded by Lieutenant-Commander Wolfgang Kaden aboard UJ116, off Texel, the Netherlands.

[12] Following research by Dennis Feary, the son of one of H49's lost crew members, he arranged for a memorial plaque to the submarine to be placed in St Mary's Church, Shotley in 2019, and a display dedicated to the sinking at the Aeronautical and War Museum on Texel Island.