This man enlisted (in 1893) as William MARSHALL, so is mis-filed in the WW1 Service Records (WO 363):

Ernest MAYERS joined the North Lancs Regiment in June 1893, deserted Jan-May 1894, served in South Africa 1899-1902, and was discharged (termination of engagement) in August 1909.
Regt No: 4036.

Born HACKNEY, declared age in 1893: 18y 6m.
Next of kin: aunt ANNE BROWN (Finsbury Park).
Married Mary Elizabeth ATKINSON in Hackney, Sept 1903.

Anc****y, MAR, pages 86336-86343