38 Group, RAF Tangmere in 1967. The balloon was about to go up on some remote island (Anguilla?) so we were all issued with war-like equipment including a tin helmet (don't know the official terminology). When it came to my turn the storeman said, without a sign of a smirk, "We don't have one in your size so here's a deficiency chit". Fortunately I never got sent anywhere and handed back all the war-like equipment a few weeks later.