Well it's a Corporal with a GCM before 1920, so he would have likely continued to wear his pre-war uniform until the transition. Very common in those days. Can of course be a pre-war image, but I don't think we can rule out the war years either Dirk MODERATOR Moderator 3,94...
Mess dress uniform is the military term for the evening dress worn by military officers in the mess or on other more formal occasions. It is also known as mess uniform and, more informally, as mess kit. It frequently consists of a mess jacket and trouser