Completed in 1906, it is best known for carrying out a successful attack on the Ottoman battleship Mesûdiye in the Dardanelles, an action for which her captain received the Victoria Cross.

It spent the remainder of its active life serving in the Mediterranean, being converted into a surface patrol boat late in the war.

[1] For surface running, the boats were powered by a single 16-cylinder 600-brake-horsepower (447 kW) Vickers petrol engine that drove one propeller shaft.

[6] In April 1915 after HMS E15 ran aground off Kephez point, B11 was one of a number of boats that failed in their attempts to destroy the wreck.

[7] On 13 December 1914, B11, commanded by Lieutenant Norman Douglas Holbrook, entered the Dardanelles and torpedoed the Ottoman battleship Mesûdiye.

After B11 hit Mesûdiye it took eight hours for the submarine to escape initially with any attempt to use the periscope resulting in heavy fire.

On 11 December of the same year the submarine under the command of Lieutenant Samuel Gravener was engaged by an Austrian flying boat.

[11] On 17 January 1916 the submarine managed to capture the crew of an Austrian flying boat after the aircraft had suffered engine failure while returning from a bombing raid.

[12] Later in the war B11 was converted to a surface patrol boat by raising the deck level and removing the electric motor.