Historia Brittonum
Problems have been identified, however, with using this source to support the "Historia Brittonum"s account. The latest research shows that the "Annales Cambriae" was based on a chronicle begun in the late 8th century in Wales. Additionally, the complex textual history of the "Annales Cambriae" precludes any certainty that the Arthurian annals were added to it even that early. They were more likely added at some point in the 10th century and may never have existed in any earlier set of annals. The Badon entry probably derived from the "Historia Brittonum".