On a summer's day in 1215 a beleaguered English monarch met a group of disgruntled barons in a meadow by the river Thames named Runnymede. Beset by foreign crisis and domestic rebellion, King John was fast running out of options. On June 15 he reluctantly agreed to fix his regal seal to a document that would change the world. A milestone in the development of constitutional politics and the rule of law, the "Great Charter" established an Englishman's right to Habeas Corpus and set limits to the exercise of royal power...