Nennius was an eighth-century historian who is a major source for tales of King Arthur. [see #56 below]. Unlike the much more careful Bede, Nennius was, as one modern historian writes “unrestrainedly inventive” [ Gerhard Herm, The Celts, [London, 1976], p. 275]. Not all of Nennius can be dismissed as he apparently had access to no-longer available 5th century sources, but neither can he be entirely trusted.
Medieval Source Book – Nennius Historia Brittonum 8th Century