William was born on 15 February 1915 in St Marylebone, London to Hungarian born Frederick (Frigyes) Steinberger and Julia nee Bainbridge and he had a younger sister Doris. Their father was listed as a managing director of a master tailors in September 1939 and their mother Julia died later the same year. Their grandparents Noe and Pepi were killed in Auschwitz in 1944.

William married Mary Flight in Hendon in April 1939 and in May 1939 he qualified as a pilot at London Air Park Flying Club. In the 1939 Register William is listed as working as a tailors cutter and a member of the Civil Air Guard.

William was on board Liberator AL554 which departed Fayid, Egypt on an operation to Tobruk. The aircraft may have been damaged by enemy fire. The aircraft ran out of fuel and one engine cut out. Unable to locate RAF St Jean in Palestine, a new course was set for Lydda, near Tel Aviv, but while attempting an emergency landing en route at about it crashed at Hadera, 20 miles south of Haifa. Six of the crew were killed and William died of injuries the following day. The wireless operator F/Sgt Cullen was seriously injured but survived.

The crew are all buried at Khayat Beach War Cemetery, Haifa, Israel. F/S David Flockhart.
F/L. N E. Sharp
F/S. W C. Stanbury
F/S. G S. Anderson
F/S. R L. Somerville
Sgt. D J. Godfrey
P/O. H C S. Cotton, RNZAF