He was the son of Bouchard de Seignelay, a family of lords of
Seignelay, and Aanor de
Montbard, a relative of
Bernard of Clairvaux. His brother was
Manassas de Seignelay,
Bishop of Orleans. During his tenure he came into conflict with
Philip II. This happened because in 1210 Philip asked the french
bishops to follow him in his campaign into
Brittany. Guillaume and his brother marched to
Mantes but not finding the king, retreated. In response, Philip confiscated their holdings, while the two bishops placed those territories under
interdict. After the arbitration of
Innocent III, in 1212 the properties were restored to the bishops and they were exonerated from military duties. Guillaume also participated in the
Albigensian Crusade with his brother, leading their troops to
Carcassonne with
Simon de Montfort. In 1220 he was elected bishop of
Paris by
Honorius III. Actually, at first,
Aldobrandino Cajetan was elected, but he refused, preferring to be
bishop of Sabina. Later,
Gauthier Cornu was proposed, but didn't receive papal approvation. This led to Guillaume's election to the post, despite his own protests. In this new post, Guillaume came again into conflict with Philip. This was caused by his affirmation of the temporal rights of the bishops of Paris over the city. This turned out favourably for Guillaume, who managed to receive an annual income from the king. Beside the king, he also entered into conflict with the
University of Paris, having to imprison and
execommunicate both students and professors due to their supposed opposition to the bishop, the
chancellor and the king. Pope Honorius, however, decreed in 1222 to free the imprisoned and asked the bishop not to molest those who had a license to teach. Guillaume was present at the funeral of Philip II in 1223, before dying himself the same year, on the 23th of November. == References ==