Duchy of Cornwall from Duchy income, assisted by Grants-in-aid from the Queen. If there is no duke (for example, if the monarch does not have any male children) the duchy income reverts to the monarch and the annual Sovereign Grant is reduced annually by the amount of the duchy's income. The duchy was established on 17 March 1337 by the Royal Great Charter out of the former Earldom of Cornwall by Edward III for his son, Edward, Prince of Wales, the "Black Prince", who became the first Duke of Cornwall. The charter established that the Duke of Cornwall is to be the eldest
Edward the Black Prince agreed, and after he had dined the prince chose twelve knights, four English, four Gascons, and four Bretons, to judge between himself and the marshal. After he had stated his case, d'Audrehem replied that he had not broken his word, for the army the prince led was not his own; he was merely in the pay of Peter. The knights considered that this view of the prince's position was sound, and gave their verdict for d'Audrehem. On 5 April 1367 the prince and Peter marched to Burgos, where they celebrated Easter. The prince, however, did not take up his quarters