Duke. The highest order of the English Nobility.
The first Duke of England, properly so called,was Edward the Black Prince, who was called Duke of Cornwall in 1337, and the first born son of the Sovereign of England is Duke of Cornwall from his birth. The title is hereditary, and a Duke's eldest son is by courtesy styled Marquess, and the younger sons Lords, with the addition of their christian name. The daughters of a Duke are styled Ladies.