Few legends have had the enduring influence of those surrounding King Arthur. Many believe the stories are based on historical truth. For others Arthur represents the archetype of the brilliant monarch reigning over a fairy-tale kingdom, offering his knights the opportunity to prove their mettle in battle and find gnostic illumination through initiation into sacred mysteries like that of the Grail. Presenting the culmination of more than 40 years' research, John and Caitlín Matthews examine the historical and mythological evidence for every major theory about the existence of King Arthur. Drawing on modern techniques in archaeology and scholarship, they reconstruct the history of the 6th century in Britain, the period when the first unambiguous references to Arthur appear. They explore the history of every Arthur candidate, the geographical arguments that have placed him in different locations and the evidence for his life and famous battles fought against the Saxons. Was the greatest British hero of all time not a king but a 2nd-century Roman officer active around Hadrian's Wall in Cumbria? A 5th-century soldier who operated in areas as far apart as Cornwall, Wales, Scotland or Brittany? Or an entirely mythical fiction that provided a figure of light during a dark period of British history? Piecing together the many fragments that constitute the image of Arthur, both the man and the myth, the authors show how each face of Arthur has something to offer and how his modern popularity proves the enduring power of the hero-myth, truly earning Arthur the title he first received in the 15th century: The Once and Future King.