According to her Wikipedia article, Amy Lyon was a very pretty girl born to a blacksmith in Ness near Neston, Cheshire and she wanted out. She left town for London and did work comparable to an exotic dancer today. Fifteen year old Emma Hart, as Amy Lyon had renamed herself, met Sir Harry Featherstonhaugh, who hired her for several months as hostess and entertainer at a lengthy stag party at Sir Harry's Uppark country estate in the South Downs. She is said to have entertained Harry and his friends by dancing naked on the dining room table. Sir Harry took Emma as mistress. She had a child by Sir Harry, after she had met Honourable Charles Francis Greville (1749–1809), second son of the first Earl of Warwick and a member of Parliament for Warwick. She became Greville's mistress. Greville persuaded his uncle, Sir William Hamilton, British Envoy to Naples, to take her off his hands. Sir William was smitten with Emma and, to Greville's shock, married her on 6 September 1791.
Lady Hamilton became a close friend of Queen Maria Carolina, wife of Ferdinand I of Naples. As wife of the British Envoy, Emma welcomed Nelson in 1793, when he came to gather reinforcements against the French. Emma reportedly flung herself upon him in admiration, calling out, "Oh God, is it possible?", as she fainted against him. Nelson wrote effusively of Emma to his increasingly estranged wife, Lady Fanny Nelson. Emma and Sir William escorted Nelson to their home - the Palazzo Sessa. Emma arranged a party with 1,800 guests to celebrate his 40th birthday. They soon fell in love and their affair seems to have been tolerated, and perhaps even encouraged, by the elderly Sir William. She had a girl in 1801, Horatia, with Nelson.