We sent a chap home once, he arranged to meet us, said he was more of a downhiller but could turn his hand to trail work. Turned up on an AMAZING bike, like one of those famous ebay monstrosiities. I *think* it was a Marin full sus, twin crown forks, full XTR and some sort of monocoque wheels. It weighed about 40lbs. Anyway he walked up the first hill, then down the first downhill. After an hour we ebncouraged him to take the road home. He turned up again but was talked out of it, I think he was a bit of a Walter Mitty type.
Then there was the guy whose light broke and we left him in the woods. In the dark. On his own. Took him 2hrs to find the car park, he was FURIOUS when we turned up. Surrey Hills aint no place for the weak..