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Cadwallon ap Cadfan (died 634) was the King of Gwynedd from around 625 until his death in battle. The son and successor of Cadfan ap Iago, he is best remembered as the King of the Britons who invaded and conquered Northumbria, defeating and killing its king, Edwin, prior to his own death in battle against Oswald of Bernicia. His conquest of Northumbria, which he held for a year or two after Edwin died, made him the last Briton to hold substantial territory in eastern Britain until the rise of the Tudor dynasty. He was thereafter remembered as a national hero by the Britons and as a tyrant by the Anglo-Saxons of Northumbria.