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 with Lancaster, who was then in Brittany. Accordingly he determined to return to Bordeaux by way of Poitiers, and after putting to death most of the garrison of the castle of Vierzon set out on 29 October towards Romorantin. Some French knights who skirmished with the English advanced guard retreated into Romorantin, and when the Black Prince heard of this he said: "Let us go there; I should like to see them a little nearer". He inspected the fortress in person and sent his friend Chandos to summon the garrison to surrender. The place was defended by Boucicault and other