There are three round barrows / cairns in this wood – this large one has been dug into in the past to leave a crescent shape. The devil originally dropped the stones here one morning when he stayed up too late, and was surprised when he heard the cock crow.
Folklore of Gwent: Monmouthshire Legends and Traditions
T. A. Davies
Folklore, Vol. 48, No. 1. (Mar., 1937), pp. 41-59.