Geoffrey of Monmouth, in Historia regum Britanniae (1135–38), adapted a story, told by the Welsh antiquary Nennius (flourished c. 800), of a boy, Ambrosius, who had given advice to the legendary British king Vortigern. In Geoffrey's account Merlin-Ambrosius figured as adviser to Uther Pendragon (King Arthur's father) and afterward to Arthur himself. In a later work, Vita Merlini, Geoffrey further developed the story of Merlin by adapting a northern legend about a wild man of the woods, gifted with powers of divination. Early in the 13th century, Robert de Borron's (Robert De Boron) verse romance Merlin added a Christian dimension to the character, making him the prophet of the Holy Grail (whose legend had by then been linked with Arthurian legend). The author of the first part of the Vulgate cycle) made the demonic side of Merlin's character predominate, but in later branches of the Vulgate cycle, Merlin again became the prophet of the Holy Grail, while his role as Arthur's counsellor was filled out; it was Merlin, for example, who advised Uther to establish the knightly fellowship of the Round Table and who suggested that Uther's true heir would be revealed by a test that involved drawing a sword from a stone in which it was set. It also included a story of the wizard's infatuation with the Lady of the Lake, which eventually brought about his death.