William the Conqueror acquired the support of the Church for the invasion of England by promising ecclesiastical reform. William promoted celibacy amongst the clergy and gave ecclesiastical courts more power, but also reduced the Church's direct links to Rome and made it more accountable to the king. Tensions arose between these practices and the reforming movement of Pope Gregory VII, which advocated greater autonomy from royal authority for the clergy, condemned the practice of simony and promoted greater influence for the papacy in church matters. Despite the bishops continuing to play a major part in royal government, tensions emerged between the kings of England and key leaders within the English Church. Kings and archbishops clashed over rights of appointment and religious policy, and successive archbishops including Anselm, Theobald of Bec, Thomas Becket and Stephen Langton were variously forced into exile, arrested by royal knights or even killed. By the early thirteenth century, however, the church had largely won its argument for independence, answering almost entirely to Rome.