"How Uther Pendragon sent for the duke of Cornwall and Igraine his wife, and of their departing suddenly again.
It befell in the days of Uther Pendragon, when he was king of all England, and so reigned, that there was a mighty duke in Cornwall that held war against him long time. And the duke was called the Duke of Tintagil. And so by means King Uther sent for this duke, charging him to bring his wife with him, for she was called a fair lady, and a passing wise, and her name was called Igraine."
Sir Thomas Mallory, Le Morte D'Arthur Book 1 (Published 1485 by William Caxton)