After a night march Grosmont attacked the French camp on 21 October while they were at dinner, taking them by surprise. There was a protracted hand-to-hand struggle, which ended when the commander of the small English garrison in the castle sortied and fell upon the rear of the French. They broke and fled. Derby's mounted men-at-arms pursued them relentlessly. French casualties are uncertain, but were heavy. They are described by modern historians as "appalling", "extremely high", "staggering", and "heavy". Many French nobles were taken prisoner; lower ranking men were, as was customary, put to the sword. The ransoms alone made a fortune for many of the soldiers in Grosmont's army, as well as Grosmont himself, who was said to have made at least £50,000 (£ in terms) from the day's captives.