HMS L27 was a L-class submarine built for the Royal Navy during World War I.

[3] For surface running, the boats were powered by two 12-cylinder Vickers[4] 1,200-brake-horsepower (895 kW) diesel engines, each driving one propeller shaft.

On the surface, the L class had a range of 3,800 nautical miles (7,000 km; 4,400 mi) at 10 knots (19 km/h; 12 mph).

[6] From 20 September 1939 to 15 January 1940, the 6th Submarine Flotilla was deployed off Skagerrak, Jutland and Horns Reef.

[8] Beginning on 22 March 1941, the Royal Navy and Allies began deploying submarines off Brest, France to prevent the German battleships Gneisenau and Scharnhorst from leaving port.