Guillaume was born in the village of Auvillars in Normandy.[4]
He was consecrated Abbot of Bec in 1399 by Guillaume de Vienne, Archbishop of Rouen. Following the king's order, he continued and completed the fortification of the abbey.[4]
He died on 3 January 1418 and was buried in the middle of the choir of the abbey.[4] His funerary slab, extracted during the Revolution, is now in the Sainte-Croix de Bernay church, which keeps it against the wall of the south transept. It was restored by Pierre-Victorien Lottin.[5]
