Do you have his army records? I see mentions of his various promotions in newspapers, and of his retirement:
"Capt E G H Green retires on account of ill-health; July 9, 1928"
The Daily Telegraph, Saturday, July 14, 1928
Also:
"The following pupils of Cheltenham College have been successful in the several entrance examinations named:- ...
Indian Army Cadetships, Wellington ... E G H Green"
Cheltenham Looker-On, Saturday, April 7, 1917