Written in 1136 by Geoffrey of Monmouth, the Historia Regum Britanniae (History of the Kings of Britain) purported to chronicle the British monarchy from the arrival of the Trojan Brutus, grandson of Aeneas, through to the seventh century AD when the Anglo-Saxons had taken control of the land. The Historia was a medieval bestseller, and copies spread across the whole of western Europe. It went on to influence great works of art and literature, being the first to outline the story of King Arthur as well as laying the foundations for King Lear and Cymbeline, both later immortalised by Shakespeare. Although it claimed to be history, the Historia has long been dismissed as an unreliable piece of medieval propaganda and national mythmaking. A new examination of the text, however, shows that it is very much more than that. In this ground-breaking new book, Miles Russell explains how individual elements of the Historia can be traced back to the first century BC, a time when Britain was making first contact with Rome. Geoffrey of Monmouth's skill was to weave these early traditions together with folklore and material culled from post-Roman sources, in order to create a national epic. In doing so, he also created King Arthur, a composite character whose real origins and context are explained here. This important new work establishes Geoffrey of Monmouth as no mere peddler of historical fiction, but as the man who preserved the earliest foundation myths of Britain. It is time to re-evaluate the Historia Regum Britanniae and shine a new light into the so-called 'Dark Ages'.