Being at least the fourth son of a noble house, William's father Thomas sought for him positions in the church which would serve to strengthen the County of Savoy rather than diminish it.

This included a request by 1220 to Henry III of England which led to William being responsible for the benefices of St Michael's on Wyre and Bingham.

William played a key role in maintaining the integrity of the county under Amadeus IV of Savoy, with the others receiving significant portions under his authority.

[4] William of Savoy lobbied to have his niece Margaret of Provence marry Louis IX of France, as this would bring prestige and influence to his family.

He and his brother Thomas accompanied her to her wedding and coronation, but William was not invited to the court in Paris and sent home by Blanche of Castile with a few gifts.

[10] When Frederick II, Holy Roman Emperor called together an army to invade Italy in 1238, Henry chose William to accompany his force of 100 knights from Gascony, so that he could lead them through his Savoy's Alpine passes.