When King John assented to the Charter of Liberties at Runnymede in June 1215, he had little thought of observing its provisions and none of laying a cornerstone of English liberties. It had been extorted under duress and his ally Pope Innocent III would assuredly annul it (which he did, three months later). But time had been gained and once the baronial opposition had been outmanoeuvred, defeated by arms if need be, the main business of his reign, the recovery of Normandy, could be resumed. Meanwhile chancery clerks were set to work penning copies of the charter for circulation throughout the kingdom. Of all the documents surviving from the Middle Ages, Magna Carta has a unique fascination...