I was at the first of these, in 67 or 68 I think, but have never been able to make it back - until this year, which I sincerely hope is not the last. As well as being one day only (21 July) it's going to be restricted on numbers too, so if you'r planning to go, visit their website and book your ticket.

(The link above didn't work for me, so here it is again: Stainsby Folk Festival.)