These stones are the remains of five men who were cheeky enough to be digging their turnips on the Sabbath. Their leader was knocked over by the shock of being turned to stone: before the beginning of the last century you could see him lying there, but he’s since been righted.
(from Grinsell’s prehistoric folklore book, drawing on a book from 1919 which I haven’t yet tracked down. I wonder if the turnips got rather specifically incorporated because of the fame of turnips in the district – the Laing’s Improved Purple-Top, don’t you know.
books.google.co.uk/books?id=4CMaAAAAYAAJ&pg=RA2-PA7)