The Legend of St. Goeznovius (1109)

After the passage of time the usurping King Vortigern, in order to guarantee support for himself for the defense of the realm of insular Britain, which he was ruling unjustly, invited some warlike men from the region of Saxony and made them his allies in his kingdom. Since these were heathenish and devilish men, who from their natures lusted to make human blood flow, they called down many evils upon the British.
Shortly afterward their arrogance was checked for a time by the great Arthur, King of the Britons, who forced them for the most part from the island or into servitude. But after this same Arthur had brilliantly won many victories in Britain and Gaul, he was finally called from human life, and the way once again lay open to the Saxons to return to the island to oppress the British, to overthrow churches, and to persecute saints.

Trans. E. K. Chambers, Arthur of Britain. London: Sidgewick and Jackson, 1927.