Tintagel, a jutting peninsula located on the north Cornish coast, was the sight of a thriving monastery during the period A.D. 470 to 500. A castle here, which bore the same name, was the site of Arthur's conception. During Arthur's rule, Mark was the overlord of Tintagel.
In the days of Uther Pendragon's rule, the castle at Tintagel belonged to Gorlois, the duke of Cornwall. It was here that Gorlois hid his wife, Igerna, whom Uther coveted for his own. In order to woo her unbeknownst to Gorlois, Merlin disguised Uther as the duke:
Called at once, Merlin, when he stood in the king's presence, was ordered to propose how the king might satisfy his longing for Igerna. Upon discovering the anguish the king was suffering because of her, Merlinmarveled at his great love and said, "To gain what you wish, you must now use new arts unheard of in your day. I know by my drugs how to give you the appearance of Gorlois, so that you will resemble himin everything. If you follow my instructions, I will make you look exactly like him, and I will make Ulfin like Jordan of Tintagel, his servant. I shall be te third, disguised as yet another, and you will be able to go to the castle for Igerna and gain admittance.
The king approved and paid close heed. After having entrusted the siege to his subordinates, he submitted to Merlin's drugs and was transformes into the likeness of Gorlois. Ulfin was also changed into Jordan, and Merlin into Britaelis, so that it was evident to no one what their apperance had been before. Then they set out fot Tintagel and came to the castle at dusk. After they hurriedly told the gatekeeper that the duke had arrived, the doors were opened and the men were admitted. For who could suspect anything since Gorlois himself was thought to be present? The king then spent the night with Igerna and satisfied himself with the lovemaking he had longed for, for he had deceived her by the guise he had assumed. He had deceived her, too, with false words that he artfully contrived. He said he had come in secret from the beseiged fort so that he might take care of the one he so loved and of his castle. Believing him, threfore, she denied nothing that he asked. This night also she conceived that the most renowned of men, Arthur, who afterward won fame by his extraordinary valor.
---excerpt from Geoffrey of Monmouth's History of the Kings of Britain
Aerial view of Tintagel, north of Cornwall. (Thomas, 1971)