Just to get back to Jane Austen: the Grand Old Duke of York who marched his men to the top of the hill was the Duke of York of her time, Prinny's brother.

BTW, I'm not certain whether or not, once a royal dukedom is given, it finishes when the holder (ie the monarch's son) dies, or whether it continues while there is still a male heir. I believe the Dukedom of Gloucester is another royal dukedom that still continues; the last Duke of Kent died without an heir, which made the title available again. I think that they have a stock of them: Gloucester, Kent, Cornwall, etc., and they recycle them.