So, I think I agree some rearrangement has taken place, the stones look wrong at present. I've been to other dolmens and thought they looked wrong too though, but I guess it could be argued they were also rearranged (or none of them were!)

I'm afraid I just don't buy the sloping inner stone though, I've not seen anything like it or seen anything like it mentioned anywhere. I know Stonehenge is unique so other unique things are possible (and do occur especially in tomb building) but it just seems so very wrong to me...