Based on fact, this is the story of William Marshal, the greatest knight of the Middle Ages, unsurpassed in the tourneys, adeptly manoeuvring through the colourful, dangerous world of Angevin politics to become one of the most powerful magnates of the realm and eventually regent of England.

From minor beginnings and a narrow escape from death in childhood, William Marshal steadily rises through the ranks to become tutor in arms to the son of King Henry II and Eleanor of Aquitaine. A champion on the tourney field, William must face the danger and petty jealousy targeting a royal favourite. Dogged by scandal, banished from court, his services are nevertheless sought throughout Europe and when William's honour is vindicated, he returns to court and wins greater acclaim and power than before.

A crusader and the only knight ever to unhorse the legendary Richard Coeur de Lion, William's courage and steadfastness are rewarded by the hand in marriage of Anglo-Irish heiress Isobel de Clare, 19 years old, the grandaughter of kings and his equal in every way.