Bela of Saint Omer was a French knight, descended from a Fauquembergues family who were castellans of the eponymous castle of Saint-Omer.
Pierre-Alexandre Monsigny was born at Fauquembergues, near Saint-Omer, in the former Artois region of France (now Pas-de-Calais), four months before the marriage of his parents, Marie-Antoinette Dufresne and Nicolas Monsigny.
Herbert and Arnulf I of Flanders joined him this time and they took Eu, but were ambushed near Fauquembergues and the king was wounded, the Count of Ponthieu killed, and many Normans left dead on the field.