I was wondering about the title, Duke of Buckingham. Apparently, it hasn't been used since 1687:
https://en.wikipedia.org/wiki/List_of_dukedoms_in_the_peerages_of_Britain_and_Ireland
https://en.wikipedia.org/wiki/Duke_of_Buckingham
Why couldn't that title be renewed for Harry? Buckingham Palace takes its name from John Sheffield, first Duke of Buckingham and Normandy (1648-1721). The palace was first a house built for Sheffield. In 1762, King George III purchased the Sheffield house for his wife, Queen Charlotte of Mecklenberg-Strelitz (she is said to have Portugese-related African heritage). After Queen Charlotte was given the house by King George III, it became known as The Queen's House. King George IV ordered the house to be converted into a palace during the 1820s.
But I guess since Buckingham is the well known name of the palace, it would never be considered for use as a dukedom again.
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