The battle occurred because of the vacillation of King Henry III, who was refusing to honour the terms of the Provisions of Oxford, an agreement he had signed with his barons, led by de Montfort, six years earlier. The King was encamped at St. Pancras Priory to the south of Lewes with a force of infantry, but his son, Prince Edward (later King Edward I) commanded the cavalry at Lewes Castle. A night march enabled de Montfort's forces to surprise Prince Edward and take the high ground here on the Downs, in preparation for battle.
The royalist army, perhaps as much as twice the size of de Montfort's, was led by Edward on the right and the King's brother Richard of Cornwall on the left, while the King himself commanded the central battalion. Having led his men out from the castle to meet the enemy, Edward gained early success, but unwisely pursued a retreating force to the north, thus sacrificing the chance of overall victory. Meanwhile, de Montfort defeated the remainder of the royal army led by the King and Cornwall. All three royals were eventually captured, and by imprisoning the King, de Montfort became the de facto ruler of England.
The King was forced to sign the so-called Mise of Lewes and though the document has not survived, it is clear that Henry was forced to accept the Provisions of Oxford, while Prince Edward remained hostage to the barons. This put de Montfort in a position of ultimate power, which would last until Prince Edward's escape and de Montfort's subsequent defeat at the Battle of Evesham in August 1265.
The fields of Landport Bottom are managed by the Lewes Community Rangers who have kindly given permission for this cache.