British E-class submarines had fuel capacities of 50 long tons (51 t) of diesel and ranges of 3,255 miles (5,238 km; 2,829 nmi) when travelling at 10 knots (19 km/h; 12 mph).

[4] On 29 June 1916, E54 left Harwich to take part in the regular patrol by British submarines near Terschelling, returning to base on 6 July.

[5] On 15 August 1916, E54 left Harwich for a patrol off the Dutch coast with the hope of intercepting Zeebrugge-bound German submarines.

[8][9] An early example of a Jolly Roger flag flown on return to port after this attack is on display at the Royal Navy Submarine Museum.

[10] From the end of March, E54, together with E32, E48 and H5, was deployed to Queenstown (now Cobh) in the South of Ireland for continued anti-submarine patrols.

[11] Later that day, an explosion was heard by E54's crew, and on going to investigate, spotted a steamer (the British ship Dorie) blowing off steam and down by the bow.

E54 picked up seven survivors from U-81 and after determining that Dorie could still make port unassisted, returned to Queenstown to land her prisoners and replenish torpedoes.

[11][12] On 16 May 1917, E54, which was now operating out of Lough Swilly, was cruising off the Hebrides when a German submarine (probably U-30) and attacked with two torpedoes that missed.

Later that day, U-30 torpedoed the British merchant ship Middlesex, which broadcast a distress signal before sinking.