Henry’s failed conquest of Naples and resulting…
1258 CE
Henry’s failed conquest of Naples and resulting debt has allowed the English barons to consolidate their power in opposition to the English crown.
De Montfort had nominally adhered to the Royal cause in 1256 and 1257, when the discontent of all classes was coming to a head.
With Peter of Savoy, the Queen's uncle, he had undertaken the difficult task of extricating the King from the pledges which he had given to the Pope with reference to the Crown of Sicily; and Henry's writs of this date mention de Montfort in friendly terms.
However, de Montfort now becomes leader of those who wants to reassert Magna Carta and force the king to surrender more power to the baronial council.
De Montfort at the "Mad Parliament" of Oxford in 1258 appears at the side of with the Earl of Gloucester at the head of the opposition, whose seven leading barons force Henry to agree and swear an oath to the Provisions of Oxford.
These effectively abolish the absolutist Anglo-Norman monarchy, giving power to a baronial council of fifteen nominated councilors and ministers to deal with the business of government and providing for a three-yearly meeting of parliament to monitor their performance.
It is said that de Montfort was reluctant to approve the oligarchical constitution created by the Provisions of Oxford, but his name appears in the list of the Fifteen who are to constitute the supreme board of control over the administration.
In return, the king receives funding from the barons. (There is better ground for believing that he disliked the narrow class-spirit in which the victorious barons used their victory; and that he would gladly have made a compromise with the moderate Royalists, whose policy was guided by Prince Edward, but the King's success in dividing the barons and in fostering a reaction rendered such projects hopeless.)