Born in 1885 in Coates, Sussex, William Alfred Clark was the fifth of seven children of William George Clark and his wife Emily. His father, who was born in Watford, was a domestic coachman and the family spent many years in Sussex.
The three oldest children had left home by 1911 and the remainder of the family had moved to 25 Chalk Hill, Oxhey in Hertfordshire. Since coach and horses was rapidly being replaced as a means of transport by motor transport, William’s father now earned his living as a tobacconist and confectioner. William, who was sixteen, was employed as a merchant’s clerk.
In 1918 William married Dorothy Ada Bish in Watford. She was a typist and shorthand writer, and was the third of five children living with her family at 45A, Villiers Road, Oxhey.