http://leylines.members.beeb.net/The%20Chiltern%20Escarpment.htm says "On the Ordnance Survey map it is defined as a hillock by the name of Chequers Knap. However, in the National Trail Guide to The Ridgeway, Aurum Press:1999, it is defined as a tumulus, and that is what it looks like. From the opposite side of Kimble Warren it is almost pyrmidal in outline. From the path immediately below it the artificial nature appears confined to the top, which seems to have been shaped, and flattened." Sorry for such a big direct quote