King Urien and Modron daughter of Avallach

In Denbighshire there is a parish which is called Llanferes, adn there is there Rhyd y Gyfarthfa (the Ford of Barking). In the old days the hounds of the countryside used to come together to the side of that the ford to bark, and nobody dared go to find out what was there until Urien Rheged came. And when he came to the side of the ford he saw nothing except a woman washing. And hten the houds ceased barking, and Urien sized the woman and he had his will of her; and then she said "God's blessing on the feet which brought thee here." "Why?" said he. "Because I have been fated to wash here until I should conceive a son by a Christian. And I am daughter to the King of Annwfn, and come thou here at the end of the year and then thou shalt recieve that boy." And so he came and he recieved there a boy and a girl: that is, Owein son of Urien and Morfudd daughter of Urien.

SOURCE

Pen. 147. trans. Rachel Bromwich. Trioedd Ynys Prydein. Cardiff: UWP, 1963. p.459.