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 returned to England, leaving John in charge of Sir Walter Manny and three other knights. He accompanied his father to Calais on 9 October to assist at the liberation of King John and the ratification of the treaty. He rode with John to Boulogne, where he made his offering in the Church of the Virgin. He returned with King Edward to England at the beginning of November. On 10 October 1361 the prince, now in his 31st year, married his cousin Joan, countess of Kent, daughter of Edmund of Woodstock, Earl of Kent, younger son of Edward I, and