Mise of Amiens The Mise of Amiens was a settlement given by King Louis IX of France on 23 January 1264 in the conflict between King Henry III of England and his rebellious barons , led by Simon de Montfort . Louis ' one - sided decision for King Henry led directly to the hostilities of the Barons ' War . The conflict between king and magnates was caused by dissatisfaction with the influence of foreigners at court , and Henry ' s high level of taxation . In 1258 Henry was forced to accept the Provisions of Oxford , that essentially left royal government in the hands of a council of magnates , but this document went through a long series of revocations and reinstatements . In 1263 , as the country was on the brink of civil war , the two parties agreed to submit the matter to arbitration by the French king . Louis was a firm believer in the royal prerogative , and decided clearly in favour of Henry . The outcome was unacceptable for the rebellious barons , and war between the two parties broke out almost immediately after the announcement of the settlement . After a victory at the Battle of Lewes in May 1264 , Montfort took over control of government , but the success was short - lived . Henry ' s oldest son Edward – the later King Edward Istarted a military campaign that ended in the Battle of Evesham in August 1265 , where Montfort was defeated and killed . Parts of the baronial resistance still held out , but by the end of 1266 the final garrison at Kenilworth Castle surrendered . The rebels were given pardons according to terms set out in the Dictum of Kenilworth . Background . By 1264 , the reign of Henry III was deeply troubled by disputes between the king and his nobility . The conflict was caused by several factors . One source of discontent was the influence two groups of royal favourites enjoyed at court : the Savoyards , relatives of Queen Eleanor of Provence , and the king ' s half - brothers , known as Poitevins or Lusignans . The native nobility were offended by the great political influence held by these foreigners . Secondly , the king had in 1254 accepted Pope Innocent IV ' s offer of the crown of Sicily for his younger son Edmund . The offer involved repelling the current Hohenstaufen rulers of the island , and proved to be very expensive . Lastly , there was a personal dispute between King Henry and one of his subjects , Simon de Montfort , Earl of Leicester . Montfort , a foreigner himself , was initially on good terms with Henry , and had in 1238 married the king ' s sister Eleanor . The two fell out , however , and Montfort became the leader of the opposition , together with Richard de Clare , Earl of Gloucester . In 1258 , Henry was forced to accept the so - called Provisions of Oxford , whereby he effectively surrendered control of royal government to a council of magnates . In 1259 the baronial program of reform was further elaborated upon in the Provisions of Westminster . The provisions remained in effect for three years ; at one point Henry ' s oldest son Edward – the later King Edward Ieven joined forces with Montfort . It was not until 1261 that Henry was able to move against the opposition . Receiving a papal annulment of the provisions , he reassumed control of government . Over the next two years , however , Henry ' s governing deteriorated the situation once more . He failed to reconcile with Montfort , and alienated Gloucester ' s son and heir Gilbert . In April 1263 Montfort returned to England after a long stay in France , and reignited the reform movement . On 16 July Henry was surrounded by rebel forces in the Tower of London , and once more forced to accept the conditions of the provisions . Prince Edward , now firmly on the side of his father against Montfort , now took control of the situation . In October Edward took Windsor Castle , and the baronial alliance started to break up . Cornered , Montfort had to accept a truce and agree to submit the issue to arbitration by the French king Louis IX . Arguments and settlement . On 28 December 1263 Henry left for France to present his case to King Louis . Montfort was prevented from attending by an accident , and he was represented by Peter de Montfort and others . Henry had already tried once before , in September , to appeal to the French king . That time Louis had been sympathetic to Henry ' s cause , but decided in favour of maintaining the provisions . At Amiens Henry argued that his right to appoint his own ministers and officials had been denied him , in violation of the royal prerogative . He also accused his opponents of destroying royal castles and laying waste to royal lands . For his injuries he demanded a compensation of the barons of £300 , 000 and 200 , 000 marks . Referring to the papal writ of annulment , Henry asked the French king to free him from observing the provisions forced upon him by the barons . Two documents survive of the barons ' complaints . In the first of these , the barons reiterated the background of the conflict , and stressed the fact that the king himself had accepted the conditions of the provisions . Henry had in fact , in an effort to gain public support , pledged to uphold the provisions , a fact that was now made the most of . The document further goes on to explain the reform instituted by the baronial council . In order to restore law and peacekeeping to the country , the council had installed a new Chief Justiciar and Chancellor . They had also appointed new sheriffs in the counties , who were to be directly accountable to the government and be replaced annually . The king had violated these conditions , it was argued , when he had appointed his own chancellor and a number of sheriffs . He had also taken over custody of Winchester Castle , which had been given over to Montfort by the provisions . Furthermore , there were accusation made against individual royal adherents , such as Roger Mortimer for his military raids in the Welsh Marches . The second document goes into more detail on the king ' s alleged transgressions . By extortionate taxation , it was claimed , Henry had impoverished the land . He had also infringed the liberties of the Church , violated Magna Carta , and corrupted justice . When Louis IX made his decision on 23 January 1264 , it was entirely in favour of Henry III . The settlement starts out by reiterating the declarations of the two parties , where they place the decision fully in the hands of the French king . Louis invoked the difficulties England had suffered over the previous years , and stressed the importance of a resolution . Since the pope had already invalidated the provisions , Louis decided to " . . . quash and invalidate all these provisions , ordinances , and obligations , or whatever else they may be called . . . " , and absolved the king from any adherence to them . Castles that were handed over to the barons as part of the agreement were to be given back to the king , and Henry should be free to appoint his own ministers . The only concession made to the barons was a general pardon extended to those involved in the conflict . The financial demands of King Henry were not mentioned . Louis was a firm believer in the royal prerogative , and was never likely to embrace the precedents set by the barons ' infringement of Henry ' s authority . There was also the papal annulment to take into account , which the deeply pious Louis was not going to ignore . At the same time , Henry ' s wife Eleanor of Provence who was Louis ' sister - in - lawhad worked hard to procure a favourable decision for her husband . It was clear from the start though , that the French king had gone too far in his partisan decision , and that the settlement was little more than a dead letter . Aftermath . The settlement did not present a solution to the conflict , but rather a recipe for further problems . The one - sided decision for the king and against the barons left Montfort with little choice but armed rebellion . Hostilities started already in February , when Montfort ' s sons , Henry and another Simon , attacked the possessions of Roger Mortimer in the Marches . Henry summoned the feudal army , and the royal forces won an important victory at Northampton , where the younger Simon was captured . Montfort was still in control of London , as Henry regained control over Kent and Sussex . Montfort marched out of London to negotiate , but the termsinvolving maintaining the provisionswere rejected by the king . The only option remaining was to fight , and the two forces met at Lewes on 14 May 1264 . In spite of inferior numbers , the baronial forces led by Simon de Montfort won the battle . Edward , commanding the right wing , quickly defeated the London forces . When he set out in pursuit of the fleeing soldiers , however , he left the rest of the royal army open to attack by the baronial forces , who soon won the day . By the settlement called the Mise of Lewes , the provisions were reinstated and Edward was given over as hostage . The government led by Montfort soon ran into problems . He negotiated a treaty with Llywelyn ap Gruffydd , the Prince of Wales , an act that made him unpopular with the English Marcher lords . In May Edward escaped captivity , with the help of Gilbert de Clare , Earl of Gloucester , who had now come over to the royal side . Edward started on a campaign of re - conquest , while Montfort was forced to suppress a rebellion in the Marches . He succeeded only by making large concessions to Llewelyn , and then moved east to join forces with his son Simon . Edward , however , routed the younger Simon at Kenilworth Castle , and on 4 August 1265 Montfort found himself trapped at Evesham , forced to give battle with a much smaller army than the royals . The battle soon turned into a massacre ; Montfort himself was killed and mutilated on the field . Even with Montfort dead resistance remained , particularly at the virtually impregnable Kenilworth Castle . In October 1266 the Dictum of Kenilworth set down terms by which the rebels could obtain pardons , and by the end of the year the garrison surrendered .