Brian of the Isles is an antagonist in Arthurian legend. Perlesvaus has Brian as ruler of Brittany and allied with Meliant against King Arthur. He invaded Britain while Arthur was on the Grail quest. he was defeated but later joined with King Claudas. It is possible to identify Brian with the historical King Bran Hen of Bryneich/Northumberland. He would have ruled from Bamburgh - which has been identified as Joyous Guard - and was also ejected from this castle, though apparently by his brother.