A historical epic
The origins of the cathedral are steeped in mystery and myth, and difficult to verify. We have to go back to the 7th century A.D. to understand the origins of the building. At that time, in the kingdom of the Franks, northern France was still largely unchristianized and had difficulty submitting to the Merovingian kings.
King Dagobert sent several bishops to evangelize the local population around 630 AD. Among them was a certain Omer, a monk from the Cotentin town of Luxeuil, who received the northernmost bishopric in Gaul, that of Thérouanne. He decides to dedicate a church to the Virgin Mary on the heights of the Sithiu hill (today’s Sithieu site). Joined bythree of his companions, Momelin, Ebertram and Bertin, Omer also helped found a monastery in 662 shortly before his death on the banks of the Aa and entrusted it to Bertin, who would become its abbot. He will be buried in the small church at the top of the town. Soon, it took the name Saint-Omer and the monastery, Saint-Bertin.
As time went by, the church of Saint-Omer became a collegiate church, becoming an important intellectual center and owning relices. With the disappearance of Thérouanne Cathedral, it will become a cathedral by housing a bishopric and will be a true Catholic bastion in the face of the emergence of Protestants from the Netherlands.