Boniface was the Prior of Nantua in 1232 along with the bishopric of Belley in Burgundy. When his father died, he received the castle of Ugine as his inheritance, and he surrendered any entitlement to any other inheritance in 1238. After the marriage of his niece, Eleanor of Provence to King Henry III of England, Henry attempted to have Boniface elected Bishop of Winchester, but was unable to get the cathedral chapter to elect Boniface. On 1 February 1241 he was nominated to the see of Canterbury. Pope Innocent IV confirmed the appointment on 16 September 1243, as an attempt to placate Henry. Boniface did not, however, come to England until 1244 and was present, in the following year 1245, at the First Council of Lyon. There, he was consecrated by Innocent IV on 15 January at Lyons, but it was only in 1249 that he returned to England and was enthroned at Canterbury Cathedral on 1 November 1249. Before he returned in 1249, he helped arrange the marriage another of his nieces, Beatrice of Provence, the sister of Queen Eleanor, to Charles of Anjou, the brother of King Louis IX of France.