Sir Henry de Montfort (November 1238 – 4 August 1265) was the son of Simon de Montfort, 6th Earl of Leicester, and with his father played an important role in the struggle of the barons against King Henry III. Henry's mother was Princess Eleanor of England, a daughter of King John, whose marriage to Simon further increased the foreign influence begun by the king, which was to result in great hostility by those very barons who later revolted against the king. Life Henry's father was Simon de Montfort, the leader of the English Barons in the Second Barons' War. Simon was the younger son of Simon de Montfort, 5th Earl of Leicester, a French noble who had been barred from his English titles and claims due to his allegiance to the French crown. Upon his father's death, the younger Simon had traded his interests in the family's French titles with his older brother for the sole possession of the English claims, and moved to England in 1229 to assert them. Becoming a favorite of Henry III, the younger Simon de Montfort received permission to marry the king's sister Eleanor of England, a jump in social status that alarmed the English nobility. In gratitude for the King's permission and support, the first son was named Henry in his honor. Second Barons' War Despite this relationship, Henry de Montfort sided with his father and the other nobles in revolt against his namesake in the Second Barons' War, with his father emerging as the leader of the rebellion and eventually the de facto leader of the nation. In January 1264, Henry was one of the deputies sent to represent the barons at the Mise of Amiens. When the Mise was set aside he commanded a body of troops despatched to secure the Welsh border. On 28 February, he stormed and sacked Worcester, and soon afterwards took Gloucester, but on Edward's approach he made a truce with him and retired to Kenilworth. With his brother Guy de Montfort, he led the van at the battle of Lewes, 14 May 1264. After the victory, on 28 May, he was made constable of Dover Castle, Warden of the Cinque Ports, and treasurer of Sandwich. When the siege of Gloucester began in 1265, Henry de Montfort and Humphrey de Bohun, holding the King and Prince Edward (later Edward I) as prisoners, spent two weeks fortifying the town