Some years ago a CAA staffer told me the biggest single cause of CAA enforcement action was aviators grassing each other up.
Often it's done for commercial advantage. One club or operator will see an infringement and get on the phone to the CAA to cause trouble for a competitor.
Often it's done by self-righteous pricks to cause trouble for the sake of it.
Once in a blue moon it's done because something dangerous is going on and there is no civilised way to stop it.
Sometimes it's so petty even the CAA get sick of it.
Our ATC friends at Glastonbury must be pretty pleased with themselves.