They are either 2/4th or 2/5th Buffs who were second line Territorials. Some of them were part of a composite battalion that went to Gallipoli with their equivalents in the West Kent’s. The remainder were on home service for one reason or another. Notice they are equipped with the old Lee Metford rifle. It is surprising that they are all mounted, given the need for horses overseas. (Information from Michael Mills, Buffs historian).
The reverse of the picture says: Grandad Bird. Harry Bird is the grandfather of Pauline Sims, he lived in Hawkhurst.
Image courtesy of Pauline Sims