On 30 March 1282 there was a popular uprising in the Kingdom of Sicily called the Sicilian Vespers, against the government of Charles I of Anjou. The noble sicilian rebels asked for Peter for help and offered him the crown as they considered his wife Constance their rightful Queen, and after receiving an embassy from the people of Palermo at Alcoy, Peter landed at Trapani on 30 August 1282. He was proclaimed King in Palermo on 4 September. Charles was forced to flee across the Straits of Messina and be content with his Kingdom of Naples. Pope Martin IV excommunicated both Peter and Michael VIII Palaiologos for providing Peter with gold pieces to invade Sicily.