On 17 December 1261, the new French Pope, Urban IV (Jacques Pantaléon), made Chancellor de Brion cardinal-priest, with the "titulus" of the church of St. Cecilia. This would have entailed Simon de Brion's residence in Rome, but the affairs of Pope Urban required that he send a representative of the highest level to France to deal personally with King Louis IX and his brother Charles of Anjou and Provence. Simon's previous experience at the French Court made him the perfect choice as Legate.