In real life, Morcar is the son of Lord Alfgar, last Mercian Earl of the Saxon era. He and his brother Edwin plotted against William after the Conquest, but Edwin’s troops killed him (Edwin) during a raid before a battle and then fought for William, a scene that is referenced early in the story.  Some months later William finally subdues the rebels of the North in an event called “the Harrowing of the North.”   Morcar is eventually captured after hiding out in the fens with Hereward the Wake, but, interestingly, was not executed by William. The rest of his life is spent as a “privileged prisoner “in Normandy.