Found the following article online, use it to answer the question: What is the name of the king whose loyalists engaged in a civil war with the baronial forces in 1264?  Henry III's reign was in crisis in 1258. He had recently suffered defeat in Wales, there were agricultural problems leading to a famine, and relations with the pope were worsening. Discontent amongst England's magnates led Henry to promise reform, but under continued pressure his authority disintegrated. A royal council of fifteen magnates was formed in June that year, and the rule of the country transferred from the king to the council. With foreign help Henry's reign was restored in 1261 as the council were reluctant to start a civil war. Simon de Montfort, Earl of Leicester, raised a rebellion. In 1264 civil war broke out between those loyal to the king and the baronial forces led by de Montfort.Rochester's constable in 1264, Roger de Leybourne, held the castle in support of Henry. John de Warenne, Earl of Surrey, was the garrison's co-commander. A baronial army led by Gilbert de Clare, Earl of Hertford, laid siege to the castle on 17 April that year. Having marched from the earl's castle to Tonbridge the army attacked from the Rochester side of the river, either the south or west. While the army advanced towards the city the royalist garrison set alight the suburbs. The king's hall within the castle was also burned down, although it is unclear why. An army under Simon de Montfort marched from London with the intention of attacking the city from another direction. The earl's first two attempts to cross the Medway were fought back, but he was successful on 18 April, Good Friday. The method used is uncertain, although it involved a fire-ship. The smoke may have been used as cover for the rebels, or the ship may have been used to burn the bridge while the army travelled by water. In a co-ordinated attack that had been pre-arranged, the armies of de Montfort and de Clare attacked the city. They entered Rochester in the evening and that night the cathedral was raided. The following day the rebels captured the castle's outer enclosure and the royal garrison retreated to the keep. Because the next day was Easter...
Henry III