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 he was taking into his pay. While his army was assembling he remained at Angoulême, and was there visited by Peter. He then stayed over Christmas at Bordeaux, for his wife, Joan, was there brought to bed of her second son Richard (the next king of England). The Black Prince left Bordeaux early in February 1367, and joined his army at Dax, where he remained three days, and received a reinforcement of four hundred men-at-arms and four hundred archers sent out by his father under his brother John, duke of Lancaster. From Dax the prince advanced via Saint-Jean-Pied-de-Port through Roncesvalles