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 already warned his father of the intentions of the French king, but there was evidently a party at Edward's court that was jealous of his power, and his warnings were slighted. In April 1369, however, war was declared. Edward sent the Earls of Cambridge and Pembroke to his assistance, and Sir Robert Knolles, who now again took service with, him, added much to his strength. The war in Aquitaine was desultory, and, though the English maintained their ground fairly in the field, every day that it was prolonged weakened their hold on the country. On 1 January 1370 the Black