Emily Hart, also called Emma Hart (PROSE: The Adventuress of Henrietta Street) or Emma Hamilton, (PROSE: Danse Macabre) was the mistress of several politicians in the late 18th and early 19th centuries.
In the 1780s, Emily was the mistress of politician Charles Greville. Without telling the Eighth Doctor or Scarlette, Juliette Vierge conducted secret alchemical experiments with Emily's help to increase her understanding of the nature of time.
Later, in 1798, Emma became famous in Britain for being the mistress of a noted Admiral from the Napoleonic Wars. (PROSE: The Adventuress of Henrietta Street) She introduced the Third Doctor to Lord Nelson at a masked ball in Naples during the Wars. (PROSE: Danse Macabre)