According to the Arthurian legends, Tintagel Castle belonged to Gorlois, the Duke of Cornwall. King Uther Pendragon lusted after Gorlois' wife, the Lady Igraine. So Gorlois placed Igraine in Tintagel Castle for safekeeping while he waged war nearby with Uther.
Merlin the Magician transformed Uther into the likeness of Gorlois so he could safely go to Tintagel and have sex with Igraine, who innocently thought her husband was visiting her. This deceit resulted in the conception of Arthur. Gorlois was ultimately defeated and killed by Uther, who then married Igraine. Apparently she held no grudge against him. Or if she did, it didn't matter.
During Igraine's pregnancy at Tintagel, Merlin bided his time and waited in his cave on the shore below the castle. When Arthur was born, Uther Pendragon immediately transferred his son and heir into Merlin's care. Merlin whisked Arthur away, placed him with a noble foster family and personally trained him to become the Once and Future King.
Again, Igraine's thoughts and feelings about these actions were seemingly not important. She definitely got the short end of the stick in this story.
Tomorrow -- Tintagel as tourist attraction.