The search for the historical figure behind what is arguably the most famous cycle of legends ever has been unrelenting over the centuries. Here, two noted Arthurian experts argue that the man whose story started the Arthurian myth was a soldier named Lucius Artorius Castus who lived at the end of the second century AD. Castus’s extraordinary career took him from one end of the Roman Empire to the other, bringing him into contact with tribespeople among the Steppe nomads – in particular the Sarmatians. For several decades the Sarmatians have been thought to be the inspiration behind Arthur’s Knights of the Round Table, among other British tales. The authors provide a fascinating detective story following the life of Lucius Artorius Castus against the colourful backdrop of the history of the reigns of Marcus Aurelius and his son, the barely sane Commodus. In doing so they reveal the manifold links between Artorius and the legend.