Acclaimed author Annette Carson continues her Richard III studies by concentrating on his brief protectorate while he was still Duke of Gloucester. Until now traditionally misrepresented, his office as Lord Protector has been poorly understood owing to an over-reliance on foreign reporters ignorant of the precise significance of this very English institution. Of equal importance, and equally disregarded, is his concurrent office as Lord High Constable of England, vested with military and judicial authority on behalf of the crown. This study reviews the development of both offices and their constitutional legitimacy in Gloucester’s hands.