The legend of King Arthur developed in the 12th century from the Celtic traditions of Wales and Armorica, the latter sources being known as the Matière de Bretagne. The fundamental text was published in 1155 by Geoffrey of Monmouth: The History of the Kings of Britain provided the true model for the Arthurian romances, with the appearance of Arthur, Guinevere, Merlin and the fairy Morgane. The legend of the Grail also developed at the same time. Here we shall discover the important role played by the seigneury of Dol-Combourg, situated in the Marches of Brittany.