Mine was at Milton Keynes in 1982
As most of you will have only seen the TV version you will be unaware of this as it was carefully edited out.
However during Brian's mega solo he runs along the stage to the right of the drums and is just about to launch into a power chord when somewhere along the trail of leads behind him they come unstuck.
So he raises one arm and swings it down onto the guitar and NOTHING!
The crowd go oooooh and arrrhh and Brian looks rather bemused as roadies rush around trying to find the break, after what seems like hours (was probably two minutes) they find it and all is well.
Brian continues where he left off and shows what a professional he is!
Wondeful stuff and very funny.
"It is better to sit in silence and have people think you're a fool, then to open your mouth and remove all doubt"