Dad got sent back from Eypres for being underage then rejoined and left after serving finally in Ireland, in 1921. He was a sergeant in the Home Guard where he taught unarmed combat.
In the picture , he is holding what looks like a riding crop and I think that must be connected with
his role with horses pulling the big guns in France.
Grandad was an RQMS, Regimental Quartermaster Sergeant.