Mis-filed (and not indexed) with the HAT names in the WW1 Service Records (WO 363):

Horace Henry HAWKES, born about 1893, address West Ham, father Henry James.
A Clerk, enlisted September 1914, de-mobbed 1919.
Reg Nos: 2641 & 590880

Anc****y, HAT, pages 14 to 27