The Duchy was created by King Edward III in 1337 to provide an income for his son, Prince Edward.
As per tradition the portfolio of assets always goes to the monarch’s eldest surviving son.
The funds support not only Charles' own household with Camilla, but also those of William and Catherine, Harry and Meghan and the princes’ grandchildren, as well as funding charitable work.
Prince William has already been preparing himself for the day he steps into his father’s shoes as the Duke of Cornwall.
Speaking on the documentary Prince Charles: Inside The Duchy Of Cornwall, William said: “Well, rest assured I’m not going to rock the boat; I’ll do much the same as what my father’s doing.
He added: “I’m not so into the architecture — that’s the only thing.”
The Prince of Wales believes that William is well placed to succeed him as the Duke of Cornwall.
Explaining that his son has had ample time to learn the ropes, which contrasted with his own experiences.
Charles said: “He's quite lucky because I found myself there at 21.
“I had a bit of baptism of fire really. He goes and visits different parts of the Duchy of Cornwall, and so he is learning, I hope, as time goes by.”