William the Conqueror brought to England the feudal system of his native Normandy. Thus, he granted land to his most important military supporters, who in turn granted land to their supporters, thus creating a feudal hierarchy.
William I was an absolute ruler but often sought the advice of the Curia Regis before making laws.
The tenants-in-chief often struggled with their spiritual counterparts and with the King for power. In 1215, from John they secured Magna Carta, which established that the King may not levy or collect any taxes (except the feudal taxes to which they were hitherto accustomed), save with the consent of this council. It was also established that the most important tenants-in-chief (the earls and the barons), as well as the ecclesiastics (archbishops, bishops and abbots) be summoned to the council by personal writs from the Sovereign, and that all others be summoned to the council by general writs from the sheriffs of their counties. John later repealed Magna Carta, but Henry III reinstated it.
The royal council slowly developed into a Parliament. In 1265, Simon de Montfort, 6th Earl of Leicester, who was in rebellion against Henry III, summoned a parliament of his supporters without any royal authorisation. The archbishops, bishops, abbots, earls and barons were summoned, as were two knights from each shire and two burgesses from each borough. Knights had been summoned to previous councils, but the representation of the boroughs was unprecedented. De Montfort's scheme was formally adopted by Edward I in the so-called "Model Parliament" of 1295. At first, each estate debated independently; by the reign of Edward III, however, Parliament had been separated into two Houses and was assuming recognisably its modern form.