It's all a bit confusing!

What I think may have happened is that the O.S. map is wrong. The circle shown isn't there. If you look at an aerial photo the field to the east of the farm shows what could be traces of an enbanked circle. When British Gas layed their pipeline in 1971, they had a copy of the O.S. map, and had a 'corridor' to work within that was about 100 yards north of the site shown on the map. If the map's wrong, then the place that should've been protected wasn't! And the pipeline tore it's way through the original, unmarked site.

So maybe the farmer's not guilty?

Just an idea...