The one in the photo is in need of repair. Unsurprising, since its not marked on any map. When they're in perfect condition they are tall and slender. They look very human, on the horizon.

The county archaeologist tells me they're medieval. When I pressed her for what evidence there was to suggest this she said "farming tradition". When I asked what she meant by "farming tradition" she stopped replying to me!

Its thought they mark the places from where shepherds watched their flocks. There's much more to it than that, though, if you ask me. For a start, you often get three right next to one another. They tend to fall on county/parish boundaries. I think they get called March Stones sometimes, in Scotland.