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 imposing this tax, had retired to his Norman estate. Charles took advantage of these appeals, and on 25 January 1369 sent messengers to the Black Prince, who was then residing at Bordeaux, summoning him to appear in person before him in Paris and there receive judgment. He replied: "We will willingly attend at Paris on the day appointed since the king of France sends for us, out it shall be with our helmet on our head and sixty thousand men in our company". The Black Prince caused the messengers to be imprisoned, and in revenge for this the Counts of