In Search of Myths and Heroes S01 E03 The Queen of Sheba

King Arthur, a 5th-century Celtic monarch who battled invading Anglo-Saxons, first appears in a history of Britain written in 830. The story was expanded in the 12th-century by Geoffrey of Monmouth, who most modern historians regard as primarily a writer of fiction. The Tudors popularised Arthur further, as did the Victorians.