Under the Capetian dynasty France slowly began to expand its authority over the nobility, growing out of the Île-de-France to exert control over more of the country in the 11th and 12th centuries. They faced a powerful rival in the Dukes of Normandy, who in 1066 under William the Conqueror (duke 1035–1087), conquered England (r. 1066–87) and created a cross-channel empire that lasted, in various forms, throughout the rest of the Middle Ages. Normans also settled in Sicily and southern Italy, when Robert Guiscard (d. 1085) landed there in 1059 and established a duchy that later became the Kingdom of Sicily. Under the Angevin dynasty of Henry II (r. 1154–89) and his son Richard I (r. 1189–99), the kings of England ruled over England and large areas of France,[W] brought to the family by Henry II's marriage to Eleanor of Aquitaine (d. 1204), heiress to much of southern France.[X] Richard's younger brother John (r. 1199–1216) lost Normandy and the rest of the northern French possessions in 1204 to the French King Philip II Augustus (r. 1180–1223). This led to dissension among the English nobility, while John's financial exactions to pay for his unsuccessful attempts to regain Normandy led in 1215 to Magna Carta, a charter that confirmed the rights and privileges of free men in England. Under Henry III (r. 1216–72), John's son, further concessions were made to the nobility, and royal power was diminished. The French monarchy continued to make gains against the nobility during the late 12th and 13th centuries, bringing more territories within the kingdom under their personal rule and centralising the royal administration. Under Louis IX (r. 1226–70), royal prestige rose to new heights as Louis served as a mediator for most of Europe.[Y]

Answer this question, if possible (if impossible, reply "unanswerable"): Who was Duke of Normandy in 1066?
William the Conqueror