The Ty-Illtud Long Barrow measures 24m by 17m, is 1.5m high and has a megalithic chamber and forecourt set in its northern part. There are incised carvings on the internal faces of all of the uprights of the chamber. These consist almost entirely of small crosses, some of them enclosed with diamonds and some with crosslets at the end of their arms. On the stone at the rear of the chamber is what appears to be a lyre of a Roman type. The carvings may be prehistoric, but some of the crosses are of a 7th to 10th century type which would fit with the tradition that the site was used by 5th - 6th century St. Illtud.

Source: Burnham. H. 1995. CADW: A Guide to Ancient and Historic Wales Clwyd and Powys. p14

Source: Briggs, C.S., 1997, An Inventory of the Ancient Monuments in Brecknock (Brycheiniog), The Prehistoric and Roman Monuments, Part i: Later Prehistoric Monuments and Unenclosed Settlements to 1000 A.D. RCAHMW, pp 31-34.

RCAHMW, February 2011