William the Conqueror gave lands to some of his more powerful supporters per baroniam, creating the Barons.

In return for rights over the granted lands, the Barons had obligations (servitium debitum).

The main two obligations were:

To provide a quota of knights for the King’s service.

Baronial Relief - a payment to the King, made once every generation when a new heir succeeded to the Barony. Traditionally 100 pounds.

In 1166, the Treasury commissioned a survey (the Cartae Baronum) to document how many knight’s service each Baron owed the King, and how those knights would be provided (from knights who were sub-tenants, holding land in return for service to the Baron, or from the Baron’s demesne – meaning knights that the Baron either employed, or members of his family, or knights he would need to hire to fulfil his service.)

For example, Lambert of Etocquigny, reported that he held 16 carucates and 2 bovates of land for the service of 10 knights. 5 knights owed him service in return for 10 of his 16 carucates of land (“enfeoffed by the old enfeoffment”, as he puts it), and the other 5 knights of his service were provided from his demesne.

The other privilege which Barons had, besides land, was the right to be called to participate in the King’s Council (Parliament) if it was held. Originally the King would send each baron a personal invitation (writ) if he decided to hold a council. Eventually, baronies fragmented and multiplied through the vagaries of inheritance and land deals, and there came to be a number of minor barons. The King’s still sent personal writs to the major barons, but only sent a general proclamation of a council (through the County Sheriffs) to alert the minor barons. The Sheriffs would then organize for the minor barons in a county to send a representative. Eventually, it dawned on the Kings that it was not really tenure per baronum which was determining attendance at Parliament, but the receipt of a writ. Kings started sending writs to people who they wanted to attend but who were not feudal barons.

In doing so, they created “barons by writ” rather than feudal barons, and started the end of the feudal system, which would eventually see nobility holding their titles by means of letters patent rather than by feudal land grant.

So, you can see that the role of Barons was changing over time in Medieval England.

In 1215, however, the Barons were still largely feudal lords, who held their lands, provided service to the Kings, and had the right to be invited to the Royal Council (Magnum Concilium). (The term ‘Parliament’ was not first used until 1236.)

The purpose of the Magnum Concilium, when it was called, in the period before 1215, was to discuss the affairs of the realm. At that time, it was not yet a legislative body. It had no explicit powers. It did not have the formal ability to accept or reject taxes. It was a way for the King to get input and feedback from his most important subjects, and sometimes a way for them to make collective decisions and plans.

1215, of course, was the date of the Magna Carta, a critical moment in the evolving roles of the Barons and the Magnum Concilium in England.

King John and many of his Barons had fallen out. The King had imposed high taxes for his wars in France, and then lost all the wars and most of his lands in France. The English Barons were disgruntled and fed up. Some of them had come out in open revolt against the King.

The King called a Magnum Concilium, to try to resolve the issues, but it did not. Suspicions went too deep. The rebels perceived King John as stalling for time. They marched on and occupied London.

Eventually, the Magna Carta was drawn up as an agreement. The King would sign it, and the Rebels would renew their oaths of loyalty.

This happened, but the accord did not last. King John got the Pope to annul the Magna Carta and war (the First Baron’s War) broke out between the King and the Rebels.

King John then died. This took some of the support away from the rebels, and the faction loyal to his son, Henry III was able to prevail.

Another Great Council was called in late 1217 to solidify the peace. This agreed on the Charter of 1217 (a modified version of the Magna Carta).

King Henry generally kept to the Charter, but there was various quarreling about how to interpret it. This eventually led to the Second Barons’ War, in 1266, wherein both sides argued that the other was breaching the charter.

Henry’s son, Prince Edward, won the Second Barons’ War, and issued the Statute of Marlborough, which included a fresh commitment to honor the terms of the Charter. All of these events helped to establish the evolving constitution of England.

The role of the Barons, however was various. Of course, their main role in all these events was as mighty subjects who could throw military strength in favor of the Rebels or the Loyalists.

Collectively, in their role as participants in the Magnum Concilium, they were not very effective. That body did not have the power to resolve the issues, and the resolution fell to war and treaties.

The body would strengthen, however, as it continued to evolve from Magnum Concilium to Parliament, though it would still be hundreds of years before the Parliament would establish itself as the supreme power in the kingdom.