Saturday night in 2010 we swerved the headliners and headed to SE corner early
Came across a queue of about 8 people outside a tent, with two fellers on the door (well not really a door, just a flap that was held closed by the blokes on the door)
every few minutes one of them would stick his head in, then say room for one more and let the next person in.
we decided to have a look seeing the queue wasn't too bad, and probably queued up for about 5 minutes.
when we were finally ushered in, we walked into a completely empty tent, only about 8 foot square, with a flap at the other side that just lead back out into the festival.
everyone who fell for it hung about for a while just to laugh at everyone else as they came through
I've no idea if this was just down to a couple of punters who found the empty tent and had a genius idea, or whether it was actually planned, but it was hilarious.