Eudaf Hen - Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth introduces Octavius as a half-brother to Constantine I, who has become King of the Britons following the death of his father Constantius. Eventually Constantine is made Roman Emperor, requiring him to leave Britain in the hands of a proconsul. Octavius, then duke of the Gewissei tribe, rebels against Roman rule, killing the proconsul and proclaiming himself king.

Constantine responds by sending three legions to Britain under the command of his great-uncle Trahern, the brother of the late King Coel. Trahern lands at "Kaerperis" and captures it, forcing Octavius to conscript all the island into the army to combat the Roman legions. Octavius engages Trahern in a field outside Winchester and is victorious. Trahern flees to Alba (Scotland) and pillages the land, and Octavious comes after him. They meet at Westmorland, and Octavius was defeated and forced out of Britain. Trahern takes the crown himself, while Octavius seeks aid from King Gunbert of Norway. In Britain, supporters of Octavius ambush Trahern and kill him near London, allowing Octavius to return to Britain. Once arrived, he scatters the Roman forces and retakes the throne of Britain, gaining an incredible amount of wealth and prestige.

Eventually, Caradocus, Duke of Cornwall, suggests that Octavius marry his only daughter Helen to the new Roman Emperor, Maximianus (Magnus Maximus), thereby uniting the British and Roman crowns. Octavius agrees, and Caradocus' son Mauricius is sent to Rome with the proposal. However Octavius' nephew Conan Meriadoc (elsewhere his son) opposes the union, and nearly attacks the arriving Maximianus. Finally Caradocus restores the peace, and Octavius abdicates the throne in favor of Maximianus.