In 1285, while Charles II of Naples, nominal prince of Achaea, was imprisoned, Robert of Artois, regent of the kingdom, named William bailiff and vicar-general of Achaea.
In 1285, while Charles II of Naples, who held a position in Achaea but was not recognized officially, was confined, Robert of Artois, serving as the kingdom's regent, chose William to act as bailiff and vicar-general for Achaea.