William began his career as treasurer and provost of the Church of St. Martin of Tours, and was elected bishop of Chalons in 1215,[1] consecrated in 1216.
The following year he became count of Perche upon the death of his nephew Thomas in the Battle of Lincoln.
[2] As count-bishop, William was a valuable advisor to the kings of France and was listed among those by Pope Honorious III to participate in the Albigensian Crusade.
[3] His death in February 1226 left the question of the succession to the County of Perche unresolved for years.
[4][5] He left money to his cousin Countess Isabelle of Chartres for the "support of the poor".