One learns the strangest things at festivals. That, for instance, this summer has been a bit of a blackcurrant disaster in the UK because the extreme heat caused all the different varieties to ripen at the same time and fall from the bushes before they could be properly harvested. That fact came from a retired Kentish farmer called Ian, next to whom we were sitting at a £65-a-head dinner at this year’s Green Man, just outside Crickhowell in Wales.