For example, Lady Camilla Osborne, the sole child and heiress of the 11th and penultimate Duke of Leeds, continues to use her courtesy title despite the fact that the title has been extinct since 1953. Her parents had previously divorced and her mother had remarried, and the distant cousin who briefly held the title as 12th and final Duke of Leeds (D'Arcy Osborne, a great friend of the late Queen Elizabeth the Queen Mother), was unmarried, there was no surviving duchess. However, if the last Duke had been married but still had no son, his widow, until she remarried, would remain Her Grace the Duchess of Leeds.
Royal examples abound in previous generations. Queen Victoria's mother remained HRH the Duchess of Kent throughout her long widowhood, for example, even though the title became extinct on her husband's death.
Thanks but I put the question because I believe the title is extinct on the death of the holder. Afterthoughts added by edit: a. I doubt she could use Edinburgh even as a form of courtesy title, the title being extinct. b. If allowed then the title could not be created again during the lifetime of a theoretical (?) holder.
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