Mis-filed (and wrongly indexed) as Williamson in the WW1 Service Records (WO 363):

Harry William DE'ATH (written as D'EATH in the Record), home address NORWICH, Norfolk. Father ARTHUR. Joined the 1st East Anglian Brigade, age 19, in April 1909. Reg No 555. Left in October 1910 to enlist in the Norfolk Regiment.

Anc****y, WIL, pages 153314 to 153317