The son of Samuel and Hannah Mason, William was born in 1899 in Wolverhampton. In 1901, he was living with his parents at 26 Raglan Street, Willenhall, along with siblings Thomas S., Caroline, Hannah J., Louisa and Gertrude. Gertude was the same age as William, so presumably they were twins. By 1911 they were at 52 Lower Lichfield Street, Willenhall, but the only children with Samuel and Hannah were Hannah, Louisa and William. As none of the children were recorded to have died, however, they were presumably elsewhere on that occasion.
William served first with the East Yorkshire Regiment (number 31434), then the West Yorkshire Regiment (number 107306) and finally with the 8th Battalion of the Border Regiment (number 29407). He was killed in action in France between 24 and 25 July 1918. He is remembered at the Etaples Military Cemetery.