"I dreamt that a tree went out of my body and grew up up to the sky; of the shadow which it threw around him, quite whole Normandy was covered." This is the way the poet Wace brings reports the premonitory dream that would have made Arlette, the girl of the tanner of Falaise, after her first night with Robert, Duke of Normandy. The columnist Benoit of Holy-Moorish add that the tree shaded not only Normandy but also "the sea and the big English ground". Nine months later was born their son, William the Bastard. In Normandy, many religious or military monuments show of this glorious epic. The three authors of this work had no other ambition than to walk on the steps of Guillaume, of his ancestors, his family and his contemporaries. Colour photos throughout