Philibert,[1] in conflict with Ébroïn, mayor of the Neustrian palace, had to leave the abbey at Jumièges near Rouen which he had founded.

He was welcomed by the bishop of Poitiers, Ansoald, whom he helped to evangelize his diocese, and then withdrew with a few monks from Jumièges to the island of Her, now Noirmoutier.

[5] The monks built a new abbey at Déas, on the shores of Lac de Grand-Lieu, after obtaining authorization from Louis the Pious, now Emperor, to divert the Boulogne river[6] in 819.

They took the relics of Saint Philbert there in 857, but had to flee again from the Normans in 862, to Messais in Poitou, on an estate donated by Charles the Bald.

In 1172, a community of Cistercian monks settled on the Île du Pilier, then obtained a charter from Lord Pierre IV de Beauvoir to establish themselves in Noirmoutier in 1205.