"The twelfth and thirteenth centuries were a time of personal monarchy, when the close friendship or petty feuding between kings and queens could determine the course of history. The Capetians of France and the Angevins of England waged war, made peace, and intermarried. The lands under the control of the English king once reached to within a few miles of Paris, and those ruled by the French house, at their apogee, crossed the Channel and encompassed...