Haven't been able to get to that session for a while but it epitomises all that's good about the folk scene. There are musicians there who will blow your socks off (including your good self if I may say so) but it can accommodate people like your young friend. If any one went along there thinking "It's only folk music so it doesn't matter, they'd learn the error of their ways very quickly or take up karaoke.

Back to Rosie's question - But if there are these mythical beasties who allegedly are ruining folk clubs by turning up week in week out, but never learn the words or keep a tune, I just want to know, what on earth do they get out of it?

I've no idea. If you ever come across one, ask them and let me know.