Good photo,
This circle is only two miles from my house but when I last visited it (feb 2010) someone has dug out beneath the central burial to a depth of around 18" and worse than simply destroying the archaeological context they have lit a fire and scraped the remnants into the hole beneath the boulder burial !
Any hope of carbon dating at this site in the future is well and truly compromised. On the brighter side the three large rocks adjacent to the south of the circle do form a natural chamber around six feet wide at the base and ten feet long which would merit investigation at some point due to their natural resemblance to a tomb and proximity to the circle.
Something is not right. This message is just to keep things from messing up down the road