Bloody awful. I'm a volunteer for the NT at Glastonbury Tor and people camping and lighting fires is a constant nuisance. No f***ing respect for the sites they claim to 'venerate.'
It's the classic catch-22. Stick railings and fences around monuments so there's no access and IMO it's not worth going to see them anyway... they're reduced to bits of stone and earth. It's a sad fact that only draconian measures would begin to control the sort of scum who do things like this.