The other text that seems to support the case for Arthur's historical existence is the 10th-century Annales Cambriae, which also link Arthur with the Battle of Badon. The Annales date this battle to 516–518, and also mention the Battle of Camlann, in which Arthur and Medraut (Mordred) were both killed, dated to 537–539. These details have often been used to bolster confidence in the Historia's account and to confirm that Arthur really did fight at Badon. 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.