They are come thither and alighted, and asked the priest what the castle was, and he told them that it was the great Tintagel.
"And how is this ground all caved in about the castle?"
"Sir," saith the priest, "I will tell you. Sir," saith he, "King Uther Pendragon, that was father of King Arthur, held a great court and summoned all his barons. The King of this castle that then was here was named Gorlois. He went to the court and took his wife with him, that was named Ygerne, and she was the fairest dame in any kingdom. King Uther sought acquaintance of her for her great beauty, and regarded her and honoured her more than all the others of his court. King Gorlois departed thence and made the Queen come back to this castle for the dread that he had of King Uther Pendragon. King Uther was very wroth with him, and commanded him to send back the Queen his wife. King Gorlois said that he would not. Thereupon King Uther Pendragon defied him, and then laid siege about this castle where the Queen was. King Gorlois was gone to seek for succour. King Uther Pendragon had Merlin with him of whom you have heard tell, that was so crafty. He made him be changed into the semblance of King Gorlois, so that he entered there within by Merlin's art and lay that night with the Queen, and so begat King Arthur in a great hall that was next to the enclosure there where this abysm is. And for this sin hath the ground sunken in on this wise."
–– Perlesvaus, or The High History of the Holy Grail (anonymous old French text, translation by Sebastian Evans)