When in my final year as an Apprentice at RAF Halton, on parade one day the "thickie" D.I. Corporal decided to inspect our rifles. Looking down the barrel of one, " What's this I see, Armstrong?". " It's corrosion Corporal". "Corrosion be buggered, it's rust"! We all "fell about" laughing, for, as Senior Entry, no one could touch us!