Shamelessly stolen from Arrse:
RSM is in his office eating a packet of jelly babies. He finds them not up to the usual standard, so jails them.
Provost sergeant goes and collects the jelly babies, and takes them back to his guardroom. Finds it funny, kicks back in his office and eats the jelly babies.
RSM visits guardroom sometime later to check on the situation, and Provo confesses he ate the jelly babies.
RSM jails Provo for eating the prisoners.