Henry had sworn again and again to observe the Charter, and his oath was no sooner taken than it was unscrupulously broken. The barons had secured the freedom of the realm; the secret of their long patience during the reign of Henry lay in the difficulty of securing its right administration. It was this difficulty which Earl Simon was prepared to solve. With the Earl of Gloucester he now appeared at the head of the baronage in arms, and demanded the appointment of a committee of twenty-four to draw up terms for the reform of the state. Although half the committee consisted of royal ministers and favourites, it was impossible to resist the tide of popular feeling. By the "Provisions of Oxford" it was agreed that the Great Council should assemble thrice in the year, whether summoned by the King or no; and on each occasion "the Commonalty shall elect twelve honest men who shall come to the Parliaments, and at other times when occasion shall be when the King and his Council shall send for them, to treat of the wants of the King and of his kingdom.

And the Commonalty shall hold as established that which these Twelve shall do." Three permanent committees were named - one to reform the Church, one to negotiate financial aids, and a Permanent Council of Fifteen to advise the King in the ordinary work of government. The Justiciar, Chancellor, and the guardians of the King's castles swore to act only with the advice and assent of the Permanent Council, and the first two great officers, with the Treasurer, were to give account of their proceedings to it at the end of the year. Annual sheriffs were to be appointed from among the chief tenants of the county, and no undue fees were to be exacted for the administration of justice in their court.

A royal proclamation in the English tongue, the first in that tongue since the Conquest which has reached us, ordered the observance of these Provisions. Resistance came only from the foreign favourites, and an armed demonstration drove them in flight over sea. The whole royal power was now in fact in the hands of the committees appointed by the Great Council; and the policy of the administration was seen in the prohibitions against any further payments, secular or ecclesiastical, to Rome, in the formal withdrawal from the Sicilian enterprise, in the negotiations conducted by Earl Simon with France, which finally ended in the absolute renunciation of Henry's title to his lost provinces, and in the peace which put an end to the incursions of the Welsh. Within, however, the measures of the barons were feeble and selfish. The Provisions of Westminster, published by them under popular pressure in the following year, for the protection of tenants and furtherance of justice, brought little fruit; and a tendency to mere feudal privilege showed itself in an exemption of all nobles and prelates from attendance at the sheriffs courts.

It was in vain that Earl Simon returned from his negotiations in France to press for more earnest measures of reform, or that the King's son Edward remained faithful to his oath to observe the Provisions, and openly supported him. Gloucester and Hugh Bigod, faithless to the cause of reform, drew with the feudal party to the side of the King; and Henry, procuring from the Pope a bull which annulled the Provisions and freed him from his oath to observe them, regained possession of the Tower and the other castles, appointed a new Justiciar, and restored the old authority of the Crown.

Deserted as he was, the Earl of Leicester was forced to withdraw for eighteen months to France, while Henry ruled in open defiance of the Provisions. The confusion of the realm renewed the disgust at his government; and the death of Gloucester removed the one barrier to action. In 1263 Simon landed again as the unquestioned head of the baronial party. The march of Edward with a royal army against Llewelyn of Wales was viewed by the barons as a prelude to hostilities against themselves; and Earl Simon at once swept the Welsh border, marched on Dover, and finally appeared before London. His power was strengthened by the attitude of the towns. The new democratic spirit which we have witnessed in the Friars was now stirring the purely industrial classes to assert a share in the municipal administration, which had hitherto been confined to the wealthier members of the merchant gilds, and at London and elsewhere a revolution, which will be described at greater length hereafter, had thrown the government of the city into the hands of the lower citizens. The "Communes," as the new city governments were called, showed an enthusiastic devotion to Earl Simon and his cause.

The Queen was stopped in her attempt to escape from the Tower by an angry mob, who drove her back with stones and foul words. When Henry attempted to surprise Leicester in his quarters in Southwark, the Londoners burst the gates which had been locked by the richer burghers against him, and rescued him by a welcome into the city. The clergy and Universities went in sympathy with the towns, and in spite of the taunts of the royalists, who accused him of seeking allies against the nobility in the common people, the popular enthusiasm gave a strength to Earl Simon which enabled him to withstand the severest blow which had yet been dealt to his cause. The nobles drew to the King. The dread of civil war gave strength to the cry for compromise, and it was agreed that the strife should be left to the arbitration of Lewis the Ninth of France. In the Mise of Amiens Lewis gave his verdict wholly in favour of the King. The Provisions of Oxford were annulled. Only the charters granted before the Provisions were to be observed. The appointment and removal of all officers of state was to be wholly with the King, and he was suffered to call aliens to his councils.

The blow was a hard one, and the decision of Lewis was at once confirmed by the Pope. The barons felt themselves bound by the award; only the exclusion of aliens - a point which they had not purposed to submit to arbitration - they refused to concede. Simon at once resolved on resistance. Luckily, the French award had reserved the rights of Englishmen to the liberties they had enjoyed before the Provisions of Oxford, and it was easy for Simon to prove that the arbitrary-power it gave to the Crown was as contrary to the Charter as to the Provisions themselves. London was the first to reject the decision; its citizens mustered at the call of the town-bell at Saint Paul's, seized the royal officials, and plundered the royal parks. But an army had already mustered in great force at the King's summons, and Leicester found himself deserted by baron after baron. Every day brought news of ill. A detachment from Scotland joined Henry's forces. The younger De Montfort was taken prisoner. Northampton was captured, the King raised the siege of Rochester, and a rapid march of Earl Simon's only saved London itself from a surprise by Edward. Betrayed as he was, the Earl remained firm to the cause. He would fight to the end, he said, even were he and his sons left to fight alone.