William was the son of Major William Henry, of the RAMC, and Fanny Sophia Brown. William was educated at Oundle School, Northamptonshire, before going on to study at the College of Medicine in 1911. He does not appear to have completed his degree, possibly leaving his studies at the start of the war.
William initially enlisted with 9th Battalion London Regiment as a Private on 1st September 1914. However he was later commissioned into the 1st Battalion Norfolk Regiment four days later as a Second Lieutenant, with whom he served in France.
William was seriously wounded by rifle fire on 10th March 1915 while fighting in St Eloi, and was subsequently sent home to recover, spending a further 45 days in hospital. Upon recovering, William reported to 3rd Battalion Norfolk Regiment on 9th June 1915. Upon finally being declared fit for active service on 6th November 1915, William returned to the continent.
He was again wounded on 28th July 1916, though was able to return to active duty by 31st July that month. William was killed in action at Falfemont Farm near Guillemont on 4th September 1916. His brother Edwin was killed in the same battle on the same day.