Article: When the Archbishop of Canterbury, Hubert Walter, died on 13 July 1205, John became involved in a dispute with Pope Innocent III that would lead to the king's excommunication. The Norman and Angevin kings had traditionally exercised a great deal of power over the church within their territories. From the 1040s onwards, however, successive popes had put forward a reforming message that emphasised the importance of the church being "governed more coherently and more hierarchically from the centre" and established "its own sphere of authority and jurisdiction, separate from and independent of that of the lay ruler", in the words of historian Richard Huscroft. After the 1140s, these principles had been largely accepted within the English church, albeit with an element of concern about centralising authority in Rome. These changes brought the customary rights of lay rulers such as John over ecclesiastical appointments into question. Pope Innocent was, according to historian Ralph Turner, an "ambitious and aggressive" religious leader, insistent on his rights and responsibilities within the church.

Question: Who said Pope Innocent was an ambitious and aggressive religious leader?
historian Ralph Turner