Ok, now I understand how that mill stone in your other posted picture ended up in the middle of no-where ;-). Bizarre scene seeing these (almost?) finished mill stones on a heap of apparent rock rubble. I wish we had more of these derelict places here in the Netherlands, like you have in the UK...
Intrigued about the mill stones Ian - I'm guessing they're not granite ?
My father has collected granite ones over the years - they fetch very high prices