It does look, in the images, as though the Sarn stone has been drilled to take a cross-shaft - presumably wooden - at some time or other. But just look how the menhir stands in relation to the Yr Eifl peaks. http://www.themodernantiquarian.com/post/32426 Reverentially ? (I don't know).

And after referring to that long-destroyed double circle on Heddon Hill, a few miles past Ponteland, I've put a circle on the map and am resolved to look at it with my pal, Dudley. Sometime. Should be able to find something associated with the original site - map shows a tumulus on the next hill.

Watch out for the Far House rock art pictures floating past - Sunday maybe - tthese are the stones the archaeologists wish weren't there !