Simplify the following text for a Grade 8 native English-speaking person.
Original: In addition there are also groups and individuals , including the Revived Cornish Stannary Parliament , the Cornish Constitutional Convention , and John Angarrack , who reject the present constitutional status of Cornwall , denying the legality of Cornwall 's current administration as a county of England , and Cornwall 's relationship to the Duchy of Cornwall .
Simplified: The Duchy of Cornwall is an estate which belongs to the Prince of Wales ( who is also the Duke of Cornwall ) but only part of it is in Cornwall .