And Merlin came up to the king and said, “Sir, I have done all I promised you. Now be sure to keep the oath you swore to me.”

The king answered, “You have made me far happier and served me far better than any man ever did another, and I will certainly hold to our bargain.”

And Merlin said to him, “I am laying claim to my reward, and I want you to give it to me. You should know that you have fathered a male child in Ygraine: this is what you have given me, and you must not have him. Any power you have over him you have yielded to me. Have the hour and night you sired him written down, and you will know whether I am telling the truth.”

Vulgate Merlin