The physician John of Procida acted on behalf of Peter of Aragon, the heir of Manfred in right of his wife. John had been a loyal servant of Manfred's and had fled to Aragon after Charles' success at Tagliacozzo. John travelled to Sicily to stir up discontent in favour of Peter and thence to Constantinople to procure the support of Michael VIII Palaeologus. Michael refused to aid the Aragonese king without papal approval and so John voyaged to Rome and there gained the consent of Pope Nicholas III, who feared the ascent of Charles in the Mezzogiorno. John of Procida then returned to Barcelona and the pope promptly died, to be replaced by Simon de Brie, a Frenchman and an ally of Charles.