The British Parliament’s origins began with the Provisions of Oxford when the barons took control of the government, key appointments and reform of common law.
English kings always summoned gatherings of ministers and barons to discuss state matters. They were known as Witans under the Anglo-Saxons or great councils (colloquia) after the Norman Conquest.
They ceased to be merely meetings of the king, his ministers, the great barons, archbishops and bishops.
A new term – parliament – began to be used from the 1230s. These impromptu meetings were replaced with a royal council with a defined constitution. This eventually became parliament’s structural core.
Henry III ruled effectively and extravagantly by lavishing expensive gifts and posts on his many foreign half-siblings and in-laws.
His foreign campaigns proved expensive, especially when he borrowed money from the pope to secure the kingdom of Sicily for his son Edmund. Henry failed so he was left with a huge debt and faced excommunication if he failed to repay the loan.
The English barons grumbled as they resented losing their power and wealth to foreigners. Henry’s relationship with his great council was increasingly strained.
They decided against a re-issue of the Magna Carta, which King John signed in 1215, as it omitted details about patronage, policy, appointments of sheriffs and offices of state.
Local knights rode from all over England when Henry summoned a parliament in Oxford on 11 June 1258. (Many arrived carrying a list of grievances and wore full armour in case of confrontations.)
The barons, led by Henry’s brother-in-law Simon de Montfort, proposed radical new scheme which became known as the Provisions of Oxford. A committee of 24 men were appointed to oversee reforms—twelve were chosen by the King whilst the nobles selected the rest.
The committee called for three parliaments per year, at set times, not when the King wanted them.
A new royal council consisting of fifteen members was created on 22 June. Henry was unable to rule without it.
The magnates demanded the reinstatement of the Justiciar’s position to dispense justice to both rich and poor. The royal chancellor and treasurer became answerable to the Council.
The King’s officers were to be appointed for specific year-long terms, appointment of local knights as sheriffs and payment of salaries.
Further reforms were included in the Provisions of Westminster, drawn up in 1259, including a clause insisting all offices of state and command of castles were restricted to Englishmen.
Henry allowed the great nobles to rule for most of two years until individual ambitions clashed and factions formed. Some magnates remained loyal to the crown whilst others looked to Henry’s eldest son, Edward, as an alternative. Most supported Simon de Montfort.
A long-awaited letter arrived from Rome on 12 June 1261. Pope Alexander IV absolved Henry from his oath to the Provisions of Oxford and annulled any initiatives introduced after 1258.
Louis IX of France pronounced judgement on the Provisions of Oxford, declaring Henry free of their restrictions in his Mise of Amiens in 1264.
Battle of Lewes
Fighting broke out between the royal army and the barons. De Montfort’s force captured Henry at Lewes on 14 May 1264. His son Edward was handed over as a hostage.
De Montfort was the virtual ruler, but he had no intention to depose the king.
He summoned a parliament in January 1265 including the nobility, knights, burgesses from the towns and representatives of the clergy. This became a landmark in England’s constitutional history.
However, Prince Edward escaped from captivity, raised a large army and met de Montfort’s army at Evesham, near Worcester, in August 1265. Prince Edward’s forces inflicted heavy losses on the opposition and killed de Montfort.
De Montfort’s reforms did not die with him. Henry’s authority was restored but the Statute of Marlborough (1267) reaffirmed Magna Carta and some of the Provision of Oxford.
Knights and burgesses met separately from the magnates and formed the House of Commons.
Edward I encouraged individuals and institutions to present petitions demanding justice or favour at parliament, and the royal council, now at parliament’s core, or its committees heard them. The amount of judicial business discharged in this way increased rapidly. Many people saw the dispensation of justice as parliament’s chief function. 
Parliament’s consent was required, for the first time, for grants of taxation. Linking taxation with representation was important in the future expansion of parliamentary power.
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