The picture shows a member of one of the infantry regiments of the Household Division of the British Army. From which of these four regiments?

Three things in the picture identify him as a member of the Welsh Guards. (1) the tunic buttons in groups of five (the Welsh Guards were the fifth Guards regiment to be raised); (2) the national symbol of Wales, the leek, on the collar and shoulder strap; (3) the white-green-white plume in the ceremonial bearskin.