Between 1941 and 1946 Hickling served as an ordinary seaman in World War II with the Royal Naval Volunteer Reserve on board "HMS La Malouine", a 29-metre French corvette taken over by the British. The ship was part of Convoy PQ 17, carrying matériel from Britain and the US to the USSR. PQ 17 sailed in June–July 1942 and suffered the heaviest losses of any Russia-bound convoy, with 25 vessels out of 36 lost to enemy action. On D-Day, he was a sub-lieutenant commanding an Mk IV Landing Craft Tank 1013 with LCT 1018 of the 43rd LCT flotilla, which carried several hundred tons of ammunition to Sword Beach, Normandy.