The Archetype of Western European Constitutions
After a series of controversial (to say the least) kings of the Plantagenet dynasty, king John ascended on the English throne. He was no longer contoversial: everybody hated him. Engaged in stupid wars in France he had destroyed the empire built by Henry II. That was the first cause of John's conflict with English barons, who have lost their properties on the continent as a result of his politics. The poverty and hunger caused also riotous discontent in cities.
As if he had not enough enemies, king John entered into an open conflict with the Pope Innocentus III. In 1207 the Pope nominated Stephen Langton as Archbishop of Canterbury and the English Primate. John was mad, because his opinion was ignored, though the Primate, according to the tradition, was supposed to be his Prime Minister. King John therefore refused the new Archbishop to enter his diocese.
In 1208 the Pope placed England under an interdict, and excommunicated king John. The results were disasterous. Due to the interdict, no christian country could trade with king John, what painfully hit English wool industry. The excommunication meant also, that everybody was dissolved from his oath of loyalty to John, thus his subjects were given a legal permission to revolt. The pope started also to assemble a war coalition consisting of Wales, Scotland and France to punish the king. Also the English self-governing cities supported Langton.
King John retreated in Langton case and allowed him finally to enter the cathedral, but this did not end the external war. Then, for the first time in English monarchy, his barons refused to fight for him. John had to hire mercenaries. In 1214 his army was routed in France.
Surrounded by conspiracies, John frantically tried to keep his throne. Everybody was against him: the cities, the pesants, the nobility. He had no more money to hire mercenaries. In early 1215 barons waged an open revolt. John had no choice but signing Magna Carta - the Great Charter of Rights.
The Magna Carta had a tremendous impact on British politics. It has introduced the famous "no taxation without representation" principle, guaranteed liberty of the Church and a right for the freemen to be judged by their equals according to the law of their land. But the most important issue was its clear declaration, that the British king is under the law, and is not superior to it.