After the battle, where [Simon] de Montfort's forces were outnumbered by two to one, he forced the unpopular King to transfer nearly all of his powers.

What followed for a year and half - before de Montfort was eventually killed and mutilated in the Battle of Evesham - was an experiment in representative democracy.

Dr Andrew Spencer, who is college lecturer at Christ's College Cambridge, said: "He was quite an impressive person and was said to have a silver tongue."

"He had great charisma and people who got onboard absolutely loved him and were loyal to the end.

"But his brashness and confidence also led many to hate him."

De Montfort was killed then mutilated in the Battle of Evesham on 4 August 1265, which effectively ended the rebellion.

De Montfort called two parliaments in 1264 and 1265, both consisting of knights and leading men who had been elected or chosen in the shires and major towns of England.

King Henry remained as head of state, but his powers were severely restricted.

David Carpenter, who is professor of medieval history at Kings College London, said: "No historian has ever been able to show a parliament which had both of these before. You could say it represented the House of Commons in its earliest form."