The 12th century collegiate church was fortified by abbott Guillaume de l’Hermite, some time between 1420 and 1430 in the Hundred Yeras’ War context, as part of the town’s vast fortification project. The main element added to the ensemble was this high defensive tower, on the central apse, equipped with several arrowslits and brattices with machicolations to shoot at assailants. A round path was added on to the north side and as were shooting stations in the towers of the transept and on the western facade.
In 1567, during the Religious Wars, the church was besieged by the Protestants, who stole its precious furniture.
In 1861, the diocesan architect Pierre Chabrol planned to have the fortified tower taken down, to give the church its original look, which was quite common at the time. However, in the end, only the towers’ shooting windows were removed.