Philip of Mahdia, a North African of berber origin, was the emir of Palermo, and successor of the great George of Antioch.
He was welcomed in Palermo as a hero cum triumpho et gloria (with triumph and glory) according to Romuald II, Archbishop of Salerno.
Following Romuald's account, he was then charged with converting to Islam and promptly imprisoned and eventually admitted guilt and he was executed by orders of King Roger, who would have forgiven such an offence against his person, but not against God.
Arab chroniclers, like Ibn al-Athir, suggest that it was because Philip had allowed several prosperous and learned families to leave Bône after capture.
Norwich finds that incredible and suggests that Roger, just months away from death, was either prematurely senile (echoing Hugo Falcandus) or incapacitated by poor health and so his ministers had Philip executed, probably for apostasy.