He was also duke of Normandy, and first monarch of the house of Anjou, or Plantagenet, an important administrative reformer, who was one of the most powerful European rulers of his time. Henry became duke of Normandy in 1151. The following year, on the death of his father, he inherited the Angevin territories in France. By his marriage to Eleanor of Aquitaine, Henry added vast territories in southwestern France to his possessions. Henry claimed the English kingship through his mother. She had been designated the heiress of Henry I but had been deprived of the succession by her cousin, Stephen of Blois, who made himself king. In 1153 Henry defeated Stephen's armies in England and compelled the king to choose him as his successor; on Stephen's death, the following year, Henry became king. During the first few years of his reign Henry quelled the disorders that had developed during Stephen's reign, regained the northern counties of England, which had previously been ceded to Scotland, and conquered North Wales. In 1171-72 he began the Norman conquest of Ireland and in 1174 forced William the Lion, king of the Scots, to recognize him as overlord. In 1164 Henry became involved in a quarrel with Thomas a Becket, whom he had appointed archbishop of Canterbury. By the Constitutions of Clarendon, the king decreed that priests accused of crimes should be tried in royal courts; Becket claimed that such cases should be handled by ecclesiastical courts, and the controversy that followed ended in 1170 with Becket's murder by four of Henry's knights. Widespread indignation over the murder forced the king to rescind his decree and recognize Becket as a martyr. Although he failed to subject the church to his courts, Henry's judicial reforms were of lasting significance. In England he established a centralized system of justice accessible to all freemen and administered by judges who traveled around the country at regular intervals. He also began the process of replacing the old trial by ordeal with modern court procedures. From the beginning of his reign, Henry was involved in conflict with Louis VII, king of France, and later with Louis's successor, Philip II, over the French provinces that Henry claimed. A succession of rebellions against Henry, headed by his sons and furthered by Philip II and by Eleanor of Aquitaine, began in 1173 and continued until his death. Henry was succeeded by his son Richard I, called Richard the Lion-Hearted.