Dawn in Lewes on 14 May 1264 breaks around four o’clock. A group of foragers out and about spots Montfort’s advancing troops and raises the alarm. Henry and Richard array their forces outside the priory and march out to the clearing in front of the city walls with the dragon standard before them. Edward, staying in the castle, is the last to get into formation. Altogether they have about 9,000 men, a quarter of them mounted, stretched out for half a mile. Montfort has a little more than half that amount, but holds back part of his men as a reserve division. It’s on the lowest, flattest part of the terrain that Edward, with the cream of the loyalist knights, starts things off with a charge that completely shatters Montfort’s left wing. All he has to do now is halt, reform his men, and drive headlong into his uncle’s exposed flank. It will soon be over after that.
But these lightly armed rebels scattering before his assault are civilian militia, Londoners, perhaps the same ruffians who abused his mother at London Bridge the year before. He can’t help but indulge in a killing spree, and so completely leaves the battlefield to hunt them down. Meanwhile, Henry and Richard’s divisions are making slow progress because of the steeper elevation and volley of stones pummelling them from slingers. Seeing Edward take off, Montfort orders his centre and right divisions to charge. They barrel into the royalist front lines with full impact. Richard’s men have barely absorbed it when Montfort throws in his reserve division. The royalist centre crumbles, and Richard, in the flight back to town, seeks shelter in a windmill. Montfort now throws everything against Henry’s division. The king takes blow after blow from sword and mace and loses two horses beneath him, but he’s able to fall back to the priory, where his household knights take up defensive positions. The fighting spills into the town. Montfort is preparing an assault on the castle when he’s alerted to a large group of horsemen approaching from the west.
It’s Edward and his knights. At the end of their pursuit of the Londoners, they noticed Montfort’s baggage train and standard at the top of the hill. Driving their horses up the slope, they killed the rearguard and surrounded the special coach Montfort had been using on account of his injured leg. They were hoping he was inside, but found several Londoners instead, supporters of the king deemed too dangerous to leave behind in the city. These loyalists tried to explain all that, but were slaughtered and the coach set alight. Only then did Edward redirect his attention to the battle below and saw what a horrible mistake he had made.
His attempt to rectify it is easily dispersed, but he and his closest comrades manage to fight their way into the priory. In doing so, he blunders for a second time that day. Henry’s trapped, but by no means beaten. He can hold out long enough for his son to regroup with reinforcements from nearby garrisons. Now they’re both stuck, and Richard, flushed out of the windmill, has been made a prisoner. The battle is over, but in order to make his victory at Lewes complete, Montfort needs the king to surrender, but Henry refuses.