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

A Northampton Shoe Trader, he joined up on 20 November 1915, declaring age 28y 5m.
Served as Pte 47423 with the Royal West Kents; Transferred to West Surreys (74016).
Named as WALTER HENRY on de-mob in 1919.

Married Violet Evelyn HARRUP in Northampton, May 1913.
Daughter VERA MAY born February 1916.
Marriage shows WALTER E CLARKE.
Possible birth (in Northampton, which is NOT stated) - WALTER ERNEST CLARK (Q1 1889)

Anc****y, CLA, pages 183512-183525