premise: King Henry III of France was assassinated by a Catholic fanatic.
hypothesis: Boniface of Savoy ( c. 1217 -- 18 July 1270 ) was a medieval Bishop of Belley in France and Archbishop of Canterbury in England . Henry III of France . In 1589 , Jacques Clément , a Catholic fanatic , murdered Henry III , who was succeeded by the King of Navarre who , as Henry IV , would assume the throne of France after converting to Catholicism , and become the first French king of the House of Bourbon . Peter of Aigueblanche ( or Peter of Aquablanca ; died 27 November 1268 ) was a medieval Bishop of Hereford .