Louis VIII (1187–1226) – the eldest son and heir of Philip Augustus – married Blanche of Castile (1188–1252), a granddaughter of Eleanor of Aquitaine and Henry II of England. In her name, he claimed the crown of England, invading at the invitation of the English barons, and briefly being acclaimed – though, it would later be stressed, not crowned – as king of England. However, the Capetians failed to establish themselves in England – Louis was forced to sign the Treaty of Lambeth, which legally decreed that he had never been king of England, and the prince reluctantly returned to his wife and father in France. More importantly for his dynasty, he would during his brief reign (1223–1226) conquer Poitou, and some of the lands of the Pays d'Oc, declared forfeit from their former owners by the pope as part of the Albigensian Crusade. These lands were added to the French crown, further empowering the Capetian family.