King Arthur and the Battle for Britannia is the last in a series of three books. The first, King Arthur: Man or Myth, weighed the evidence for and against a historical figure. The second, The Battles of King Arthur, looked in detail at the famous battle list from the Historia Brittonum. Having looked at the questions of whether and where, this final book takes on the different question of who was Arthur? The book is intended to save readers time and money wading through the scores of competing theories. It explains the problems with many of these theories to date, their failure to gain widespread support and why many historians remain sceptical about the existence of a historical Arthur.

There is however a reasonable consistency in medieval genealogies and a good reason why Arthur does not appear in any of the list of kings of early kingdoms. Instead he is placed in the context of a fragmenting post-Roman provincial structure, alongside the emergence of petty kingdoms with new cultural identities. A heroic Brythonic culture in the west and north and a Germanic culture in the east and south.

The book looks at the evolution of the legend comparing the chivalric French Romances with the Arthur of the darker Welsh tradition. A mythical figure may have emerged from the mead halls and war band culture of the sixth century. However the book describes how a historical figure may have been mythologised and who such a warrior may have been.