Last week was the worst I've ever heard entering London. 121.5 has 2/3 idiots competing who could play the more ridiculous music over freq for about 5 minutes.
I then heard a transmission for Norwegian on London freq and they responded to it on guard. Someone else replies "Gotcha"... silence... I guess that'll have to do for justice.
My theory is that it doesn't happen when there are 2 idiots in the flight deck, just one when the other person goes for a piddle.