At Gaer Llwyd, about half way between Chepstow and Usk, is a cromlech—I believe the only one in Monmouthshire—the origin of which is thus accounted for by popular tradition.
“Once upon a time,” which may be token to mean in the heroic ages of Gwent, there lived one Twm Sion Catti, who was on more familiar terms than a Christian gentleman (if he was one) ought to have been with his Satanic Majesty, with whom he one day engaged in a friendly game of quoits. It seems to have been a trial as much of strength as accuracy of aim, for the quoits consisted of the stones which now form the cromlech. A believing imagination points out the steps by which each cast was matched by another as good, until on Twm Sion Catti throwing a stone which literally capped them all, and now measures upwards of twelve feet by four, his adversary gave in.
Now, as there was a Tim Sion Catti who flourished in historic times—a kind of Welsh Robin Hood of the period of Queen Elizabeth—we must suppose that tradition, with its usual readiness to group all marvellous actions around one popular hero, has confounded his name with an earlier one associated with the cromlech.
From Notes and Queries, July 27th, 1878, our correspondent being J F Marsh.