This man enlisted as CLARKE, so is mis-filed in the WW1 Service Records (WO 363):

William Henry SAUNDERS, a Motor Driver by trade, enlisted 17 March 1915 with the ASC (Regt No. 053979). Served until at least 1919.

Declared age 1915: 39y.
Home address: Finsbury Park, London.
Married 1906 at Islington: Lottie Loretta WELCH (freebmd shows Lottie Laurietta).
Children: Walter William 1908, Bessie 1910, Frank Albert 1914, Gladys Mary/May 1917.

Anc****y, CLA, pages 183776-183780

OOOPS! - This may be a repeat posting. My files show him as pages 2-47, same details, discharged 1920