At an early age, he entered the Abbey of Luxeuil, where, under the austere rule of its abbot, Columbanus, he prepared himself for a future missionary career.

About the year 638 he set out, in company with two confrères, Mummolin and Ebertram, for the extreme northern part of France in order to assist his friend and kinsman, Bishop Omer,[1] in the evangelization of the Morini.

This country, now in the Department of Pas-de-Calais, was then one vast marsh, studded here and there with hillocks and overgrown with seaweed and bulrushes.

On one of these hillocks, Bertin and his companions built a small house and they went out daily to preach the Christian faith to the natives, most of whom were still pagans.

[3] The community grew so rapidly that in a short time this monastery also became too small and another was built where the city of St. Omer now stands.

Mummolin, perhaps because he was the oldest of the missionaries, was abbot of the two monasteries until he succeeded the deceased Eligius as Bishop of Noyon, about the year 659.

The monks were expelled in 1791 by the invading forces of the French Revolutionary Army and in 1799 the abbey and its church were sold at auction.