His story was recorded by his Christian contemporaries Romuald Guarna and Hugo Falcandus from Sicily and the Muslim historian Ibn Khaldun.
During the reconquest of Roger I's "Kingdom of Africa" by the Muslims (1159), Peter led 160 ships in a raiding expedition to the Muslim-held Balearic Islands.
While Arabic sources credit a gale with dispersing the fleet, Hugo Falcandus asserts that Peter was "only in name and dress a Christian, and a Saracen at heart".
In 1162, Peter replaced the deceased Count Sylvester of Marsico in the triumvirate of officials—including Matthew of Ajello and Richard Palmer—in whom the king had confided the administration of the realm since the assassination of his prime minister, Maio of Bari, in 1160.
On her husband's death in 1166, the queen dowager Margaret of Navarre assumed the regency for her young son William II.