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 the Battle of Nájera. However, after a wait of several months, during which he failed to obtain either the province of Biscay or liquidation of the debt from Don Pedro, he returned to Aquitaine. Prince Edward persuaded the estates of Aquitaine to allow him a hearth tax of ten sous for five years in 1368, thereby alienating the lord of Albret and other nobles. Drawn into open war with Charles V of France in 1369, he took Limoges, where in 1370 he gave orders for an indiscriminate massacre in revenge for the voluntary surrender of that town to the French