The bloke concerned would say he was ignorant of the site being there - but he knew full well what it was (that's assuming it definitely was him - though if not, who the hell was it!?). On the occasion he ranted at me about being sat eating some sarnies in the circle & I asked about the oil-drums being there, along with some remarks about reporting the guilty party - and certainly then he was aware of its megalithic status. Let's hope your letter has some effect.
It's weird - look at all the attention given to Rollright when paint's been splattered all over it. But the complete destruction of a circle up North seems to be treated in a wholly different manner. Hmmmm... that's given me an idea...