Geoffrey of Monmouth was a twelfth-century Anglo-Norman historian who wrote a number of hugely important books. Works such as the Prophecies of Merlin and the History of the Kings of Britain established his reputation as one of the foremost chroniclers of the age.

It is in the latter of these two books that Geoffrey writes about Arthur Pendragon, the legendary British king. But Geoffrey doesn't treat Arthur as a legendary figure; he writes about Arthur as a real person, someone who actually existed.

This approach distinguishes Geoffrey's account of King Arthur's life from other accounts that treat him as a legend. Even so, by modern-day standards of historical scholarship, the History of the Kings of Britain doesn't pass muster as a work of history. It weaves together a variety of colorful myths, tales, and legends in its attempt to provide an account of Britain's historical origins. For instance, Geoffrey tells us that Britain was named after Brutus, a descendant of the Trojan hero Aeneas.

Geoffrey claimed to have derived his account of King Arthur's life and reign from an old book that he had received from a cleric called Walter, Archdeacon of Oxford. But this by no means validates the contents of his History of the Kings of Britain. Geoffrey may well have believed that he was providing his readers with an authentic historical account of Arthur and his reign, but the evidence suggests otherwise.