Those that were in the garrison at Cassel set out one day, about vespers, with a design to defeat the king and all his army. They marched very quietly without noise in three divisions; the first of which advanced straight to the tents of the king, and was near surprising him, as he was seated at supper, as well as his whole household. The second went to the tents of the king of Bohemia, and almost found him in the same situation. The third division attacked the quarters of the count of Hainault, and nearly surprised him: they pressed him so closely, that he and his people had scarce time to arm themselves; and the lord of Beaumont, his brother, and his company, were in a similar situation. All the three divisions came so quickly up to the tents, that neither the lords nor the soldiers had time to assemble or properly arm themselves, and they would all have been slain, if had not been, as it were, a miracle of God: but, by his grace, each of these lords defeated their enemies, and so completely, that, in the space of an hour, out of twelve thousand Flemings not one escaped. Their captain was also killed. Nor did any of these lords receive any intelligence of the other until the business was finished. Of all the Flemings not one turned his back; but they were all slaughtered on the spot and lay in three large heaps, one upon the other. This battle happened in the year of grace 1328, on St. Bartholemew's day.
The French came then to Cassel, and placed there the banners of France, the town having surrendered to the king. Afterward Poperinque, then Ypres, and all the castlewick of Beruges followed, and received the count Lewis their lord, and swore fidelity and loyalty to him for the time to come. The king soon set forth with his troops towards Paris, where, and in the neighbourhood, he staid some time. He was much praised and hounoured for this enterprise and for the service he had rendered to the count Lewis, his brother. He lived in great prosperity, and increased the royal power. No king of France, it was said, had ever kept so royal a state as king Philip.