Just a guess. This is the end of their recruits' course. They are wearing their capbadges, which means they have passed their saluting test - normally towards the end of the course. And their battle dress is severely pressed, another sign that this is at the end of basic training.
National Service was beginning to wind down at this point. It was decided that those born on or after 1 October 1939 would not be required, but conscription continued for those born earlier whose call-up had been delayed for any reason. In November 1960 the last men entered service, as call-ups formally ended on 31 December 1960, and the last National Servicemen left the armed forces in May 1963.
Details from the Imperial War Museum
