Monitoring guard a few weeks ago, only able to hear one side of the conversation between London and an unknown ac:
ATC: Last station this is London Centre, you're on guard.
(silence)
ATC: Last station this is London Centre, you're still on guard.
(silence)
ATC: Last station this is London Centre, I don't know who you are or why you're chatting on guard, but I have your expletives on tape...
