Are there actual provisions for that or would he have to waive his right?
I would think there is always the caveat that a deal is voided if the person assigned with the duty is seen to be severely and chronically incapacitated from this point forward. Failing that, Charles could be ‘convinced’ to abdicate if under duress, real or presumed. There may be a variety of ‘undisclosed scandals’ that can be used to make the water of public life a very hot and uncomfortable place, even for a Prince.