The title Duke of Normandy was given to the rulers of the duchy of Normandy. This fief was created in 911 by Charles the Simple King of France for Rollo, a leader of Northmen. In 1066 the seventh duke, William II, became King William I of England. The title of Duke of Normandy was held by the Kings of England until Henry III gave up the title by treaty in 1259. King John had lost mainland Normandy in 1204, and kept only the Channel Islands. Today the Channel Islands are a British Crown dependency.