Lady Margaret Cavendish (1661 Р1716) married John Holles, 4th Earl of Clare (1662 Р1755) and this marriage made them the wealthiest couple in England. Holles requested a dukedom from the King, and the Dukedom of Newcastle upon Tyne was created for him.

Image: Lady Margaret Cavendish, Duchess of Newcastle, Sir Godfrey Kneller (?), 1683.