Thanks to that ecclesiastical control of some of the most prosperous cities north of the Alps, like Arras and Ypres, the bishopric was able to build a cathedral which was at the time the largest in France.
But then Lambert, the Abbot of Saint-Bertin held an election carried out by the clergy and laity of the diocese, which produced Jean de Warneton, who was a Canon of Lille and a religious of the monastery of Saint-Eloi.
Urban II wrote to the Metropolitan, Manasses of Reims, ordering him to have the clergy and people present Bishop-elect Jean to the Bishop of Arras for ordination to the priesthood.
[1] In 1303, there had been a fire in Thérouanne, as a result of the marauding and pillaging of some nobles and clerks during war in Flanders, which had led to murder and desecration of churches and cemeteries.
On 8 March 1304 Pope Benedict IX authorized the Chapter of Thérouanne to use the money left by Bishop Henri de Murs for the establishment for a prebend in the Cathedral for the purpose of repairing the church of Nôtre-Dame which had been damaged in the fire.