I disagree. they are named for the cities. The Cities were separate from the surrounding areas - counties were not defined as they are now.
The other city dukedoms - still existing - Lancaster (HMQ), St Albans; Manchester
And others not related to specific cities or counties - Marlborough (v small town); Beuafort (family of John of Gaunt); Wellington; Abercorn; Grafton and Richmond, Lennox andGordon.
I still hold out for an ancient kingdom - Duke of Mercia. A great regiment and a noble history.
Um, No. The kingdom of York, and later duchy and now county of York has existed since before William the conqueror. The first Duke of York owned estates in Yorkshire, and when he was elevated to Duke, he was named Duke of York because of those estates in Yorkshire, not the city itself. The house of York is descended from him. Now the title is of course not actually attached to the land in any real way, nor the city.
The same with the Duke of Lancaster. The Duchy of Lancaster doesn't refer to the city of Lancaster, but the holdings of the duke which in no way are limited to the city of Lancaster (this is where the queen gets most of her income). The duchy owns numerous estates, spread throughout Lancashire, not simply Lancaster castle.
Cambridge was created on the same principal, referring to the area and not simply a city. These cities are the heart of the country, why they are named after them. They serve now as the political seat,they once served as a family seat in the days when titles had power.
So Albans, Edinburgh Manchester. Again I didn't say there weren't, said they were rare.
Some of the others came as the Dukes were elevated from lower titles. The Earl of Lennox, for instance. They just upgraded his title to Duke, which is why it doesn't fit the rule. Others were a connection again to their private estate or in the case of Gordon and Beaufort, their family name.
I guess Harry could be the Duke of Windsor or Duke of Mountbatten. Duke of Kennsington for the palace he grew up in???
No he is more likely to be given either a current county or one of the older ones (Wessex no longer exists so an old one is possible).