King Arthur is one of the most controversial topics of early British history. Are the legends based on a real historical figure or pure mythological invention? Ilkka Syvanne’s study breaks new ground, adopting a novel approach to the sources by starting with the assumption that Arthur existed and that Geoffrey of Monmouth’s account has preserved details of his career that are based on real events. He then interprets these by using ‘common sense’ and the perspective of a specialist in late Roman military history to form a probable picture of what really happened during the period (roughly AD 400-550). This approach allows the author to test the entire literary evidence for the existence of Arthur to see if the supposed events of his career match what is known of the events of the period, the conclusion being that in general they do. Arthur’s military career is set in the context of the wider military history of Britain and Europe in this period and along the way describes the nature of armies and warfare of the period.