In the war between the two surviving sons of William the Conqueror, Raoul III chose to support the younger brother, Henry I "Beauclerc", recently crowned king of England. On Raoul III's father's death in 1102, he crossed the Channel to take up his father's possessions in England, rallying to Henry and thus allowing himself to make a good marriage to Adelise, daughter and heiress of the Anglo-Saxon earl Waltheof of Northumbria.
From 1104, Raoul accompanied Henry in his campaign to conquer Normandy. After the battle of Tinchebray (1106), the campaign led to the imprisonment of duke Robert Curthose and his replacement by Henry, thus re-uniting England and Normandy under one master as it had been at the time of William. Raoul III's support for Henry was confirmed during the revolt of the barons of eastern Normandy against Henry in 1118-1119. Raoul did not rally to the rebels. Throughout the revolt, if Orderic Vitalis is to be believed, he appears to have remained neutral or flexible in his allegiances. The leader of the revolt (Raoul's uncle Amaury III of Montfort) explained to king Louis VI of France that he had to attack Normandy from the south east since Raoul III was helping them. Amaury assured him that Raoul would join his vassals with Louis's troops and open four castles to him: Conches, Acquigny, Portes, Tosny. In autumn 1119, Louis VI decided to intervene but the events that followed showed that Raoul III was not backing up Louis's force as Amaury had hoped and was not a sure supporter of the revolt. Raoul II de Gaël, one of Henry's supporters, suspected the Duke of Tosny of wanting to capture him. On Henry's advice, he conceded him Pont-Saint-Pierre and Val de Pîtres to keep him loyal
In 1123-1124, Amaury de Montfort began another revolt against the king, during which Raoul III remained loyal.
Father : Raoul II of Tosny