The Medieval period
In 1215, an alliance of aristocracy, church and merchants force King John to agree to the Magna Carta, a document in which the king agrees to follow certain rules of government. Later kings frequently confirmed and reissued this document, the most famous in English constituional history; it was sometimes referred to as the Great Charter of the Liberties of England. In fact, neither John nor his successors entirely followed them, but the Magna Carta is remembered as the first time a monarch agreed in writing to abide formal procedures. Although Magna Carta did not settle the conflict between John and his barons, it soon came to be regarded as the fundamental cornerstone of English constitutional law.