Mabinogi myths from the Red Book of Hergest (written pre-13c, incorporating pre-Roman myths of Celtic gods):
Gereint vab Erbin. Arthur a deuodes dala llys yg Caerllion ar Wysc...
(Geraint the son of Erbin. Arthur was accustomed to hold his Court at Caerlleon upon Usk...) (from Myth)
Opening lines of one of the