Lady Pemberton is based on Elizabeth Herbert, Countess of Pembroke
  and Montgomery. She was the daughter of Elizabeth Trevor and Charles
  Spencer, 3rd Duke of Marlborough.  In 1760, the Countess of Pembroke
  became the Lady of the Bedchamber to Queen Charlotte, a duty which
  the fictional Lady Pemberton shares.

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 John "Gentleman" Jackson, the former heavyweight champion of 
 England  and the teacher of the "Sweet Science" to the members of the
 Ton,  makes his appearance in Lord Wellesbourne, indirectly.
 Wellesbourne is one of his students. 

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Henry Angelo had a Fencing Academy on Bond Street near John "Gentleman" Jackson's boxing club. He, too, makes an indirect appearance in the book as Wellesbourne frequents Angelo's fencing academy also.

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