This collection represents the surviving output of the clerks of the men and women of the most powerful magnate dynasty in England, Wales and Ireland in the thirteenth century. Its greatness was short-lived, but as a result of the Marshals' spread of interests and marriage alliances the charters and letters edited here embrace a remarkable diversity of lordships and societies. That fact and the central place the two Earls William Marshal held at the court of the young Henry III between 1216 and 1231, playing a decisive role in the establishment of Magna Carta, give this collection a unique interest for medieval historians of Britain and France, more so perhaps than for any other contemporary magnate family.