On Duke Robert's death in 1085, Peter recognised Roger Borsa as his successor and in August 1086 accompanied him on his visit to Sicily, which was then in the process of being conquered by the Normans from its Muslim rulers. He attended the ducal court again in 1092, witnessing a charter of Duke Roger, but the remoteness of Lesina in northern Apulia seems generally to have kept him out of the civil strife of the kingdom, into which his brother Amicus was frequently drawn.