William Arthur Allsopp was born on 13 May 1918 at Tamworth, New South Wales to Harold Allsopp and Imelda Gladys Connor. He worked as a clerk, a storeman and an electrical apprentice before applying for the Royal Australian Air Force crew in early July 1940.

On 1 August 1940, Allsopp enrolled in the RAAF reserve at Tamworth and enlisted at No.2 Rec Centre in Sydney, New South Wales on 31 March 1941. He was attached to the 35 Squardon, Royal Air Force and underwent training in Canada and the United Kingdom. On the night of 25/26 July 1942, Allsopp was an air gunner on board the Halifax W1147 during an operation to attack Duisburg, Germany. After failing to return, he was declared missing; his status was changed to missing presumed dead in April 1943. Only one of his crewmembers survived, returning to England in September 1942 and reporting the crash of their aircraft.

After the war, Allsopp’s remains were located and identified then interred at Jonkerbos War Cemetery, Netherlands on 4 December 1947.