The following Easter, at the coronation feast, King Uther fell in love with Ygraine, wife of Gorlois, Duke of Cornwall. He lavished attention on her, to the scandal of the court; she made no response, but her husband, in fury, retired from the court without leave, taking his wife and men-at-arms back to Cornwall. Uther, in anger, commanded him to return, but Gorlois refused to obey. Then the King, enraged beyond measure, gathered an army and marched into Cornwall, burning the cities and castles. Gorlois had not enough troops to withstand him, so he placed his wife in the castle of Tintagel, the safest refuge and himself prepared to defend the castle of Dimilioc. Uther immediately laid seige to Dimilioc, holding Gorlois and his troops trapped there, while he cast about for some way of breaking into the castle of Tintagel to ravish Ygraine. After some days he asked advice from one of his familiars called Ulfin. “Do thou therefore give me counsel in what wise I may fulfil my desire,” said the King, “for, and I do not, of mine inward sorrow shall I die.” Ulfin, telling what he knew already—that Tintagel was impregnable—suggested that he send for Merlin. Merlin, moved by the King’s apparent suffering, promised to help. By his magic arts he changed Uther into the likeness of Gorlois, Ulfin into Jordan, Gorlois’ friend, and himself into Brithael, one of Gorlois’ captains. The three of them rode to Tintagel, and were admitted by the porter. Ygraine taking Uther to be her husband the Duke, welcomed him, and took him to her bed. So Uther lay with Ygraine that night, “and she had no thought to deny him in aught he might desire.” That night, Arthur was conceived.

But in the meantime fighting had broken out at Dimilioc, and Gorlois, venturing out to give battle, was killed. Messengers came to Tintagel to tell Ygraine of her husband’s death. When they found “Gorlois”, apparently still alive, closeted with Ygraine, they were speechless, but the King then confessed the deception, and a few days later married Ygraine.