Emma Hamilton (1765–1815) was born into poverty. Through the sheer force of her indomitable personality and her wit, she became one of the most celebrated women in England – friends with royalty and other influential members of society. From her earliest years, she was a creative, imaginative muse, whose portraits by George Romney (1734–1802) and others shine with a spectacular luminosity; she is both eighteenth-century woman and a classical figure in one.

Emma was a political operator, a diplomat, a woman who used her intelligence and skill to influence the course of war, a pioneer of the arts, and an actress ahead of her time. And yet she died in poverty, not quite 50, and afterwards was castigated by Victorian society as a blot on her lover Lord Nelson's (1758–1805) memory.

Emma was born Amy or Emy Lyon in Ness, Cheshire, in 1765, into a hard life. Her father, a blacksmith, died when she was a baby, so she was raised by her mother and grandmother in north-east Wales. Emma went into service as a girl but headed to London in 1777, and there found a respectable position as a maid for a doctor; later she may have worked at the fashionable brothel run by Mrs Kelly in Arlington Street. Emma found herself attracted to the stage.

By the time she was fifteen, she was a mistress to a young aristocrat, Sir Harry Fetherstonhaugh (1754–1846). After she fell pregnant with his child, he abandoned her.

Emma begged one of Sir Harry's friends, Charles Greville (1749–1809), to help her. He agreed to take her as a mistress and set her up in a house in Edgware Row. She would have the baby – a girl she called Emma – and send it off to be boarded in the north. And she changed her name, to Mrs Emma Hart. Greville was determined that none of her old friends or associates would find her.

Not long after she had given birth to her daughter, in 1782, Greville took her to George Romney to sit for her portrait; he was determined to turn her to profit. Romney, by then close to 50, had left his home in the Lake District to make his way in the world; he had travelled to Italy and returned to make his visions a reality. But he felt excluded by high society and the Royal Academy and felt a strong rivalry with fellow painter Joshua Reynolds (1723–1792).

Emma arrived at his studio, and he was immediately captivated by her grace and skill. She was so young, barely 17, but a genius at embodying moods and styles. One of the earliest paintings Romney made of her was as Nature. Emma, holding the studio dog, is the image of youth, freshness and beauty.

1782, oil on canvas by George Romney (1734–1802)

It was the beginning of a remarkable artistic collaboration between painter and model, with Emma an active participant. Romney painted Emma again and again, producing dozens of portraits, probably more than 70, having her embody goddesses and styles. He displayed these paintings in his studio, essentially an open house, to the delight of his society visitors.

One of Romney's most fabulous portraits of Emma depicts her as Circe, a full-length portrait in which she holds up her hand, turning men into swine.

Emma Hart (c.1765–1815), Lady Hamilton, as Circe

The woman from nowhere had become one of London's greatest models. In a time when acting was often extremely flamboyant due to the levels of noise in the audience, Emma showed emotion through the movement of an eye, through stillness – her direct gaze was so uncompromising. London was hungry for portraits of beautiful women but few wanted to sit for them.

Emma Hart (c.1765–1815), Lady Hamilton, as Calypso

With Emma, Romney had struck gold – a genius model, with an infinite capacity for work. Emma wanted to please Greville, and she knew it was expected of her, but she was also devoted to the work and to Romney himself.

Emma hoped she would marry Greville but he was growing weary of her. He finally persuaded his uncle, Sir William Hamilton (1730–1803), the British Ambassador to Naples, to take her, at least for a time. Greville lied to Emma and told her he was sending her to Naples to acquire a European polish, and then he'd marry her. Emma arrived in Naples on her 21st birthday in April 1786, to be told by Sir William that Greville was never going to marry her and she was expected to be Sir William's mistress.

Emma was devastated at how she had been betrayed. Sir William treated her kindly, as a favourite niece, and an affection developed between the two; she eventually became his lover. In Naples, Emma was surrounded by classical objects Sir William had collected. She had lessons in the arts, learned Italian and French, and was painted by all the great painters, including Élisabeth Louise Vigée Le Brun (1755–1842) and Angelica Kauffmann (1741–1807).

In one of her iconic portraits by Vigée Le Brun (who also painted her as a Sybil and as a bacchante or Ariadne), Emma's hair is flowing, Mount Vesuvius is smoking behind her, and she is dancing in one of her famous 'Attitudes'.

Lady Hamilton (1761–1815), as a Bacchante

The 'Attitudes' were a performance developed by Emma, with Sir William, to entertain his guests – many of whom were travellers on their Grand Tour – at his beautiful home in Naples. Emma, moving between poses from classical artworks, using scarves and drapes, used her expressive face to embody a variety of moods – from the Greek figure of Niobe weeping over the death of her children, to a bacchante. Her brilliance at expressing emotion through a single movement captivated the onlookers, including the German writer Goethe (1749–1832).

On visiting Naples in 1791, the artist Friedrich Rehberg (1758–1835) captured some of Emma's poses in a series of line drawings, shown here in a print after the original.

Emma Hamilton in Greek costume and assuming one of her famous 'Attitudes'

In 1791, when Emma was 26, she and Sir William returned to London to marry. On the morning of her wedding, she sat for her wedding portrait by Romney – it was the only portrait in which she was herself, not a mood or a goddess. After the wedding, at St Marylebone Church, she returned to sit once more.

1791, oil on canvas by George Romney (1734–1802)

During their four-month stay in London, Emma also sat for Thomas Lawrence (1769–1830), who made this drawing of her in profile.

In Naples, she cemented her friendship with the Queen, Maria Carolina (1752–1814), acting as an effective diplomat between her and Sir William. When Napoleon (1769–1821) was threatening Naples, Emma wrote an astonishing letter to Lord Nelson, who had recently beaten Napoleon's navy at the Battle of the Nile. Emma used all her political skills to persuade him to come to Naples to protect her beloved Queen from Napoleon. Nelson arrived in 1798. He was entranced by Emma and the two fell in love, even though they were both married. Sir William accompanied them – and the three liked to celebrate their unity.

Nelson (1758–1805), and Lady Hamilton (1765–1815)

After a series of scandals, including the brutal quelling of a rebellion in Naples, the government recalled both Nelson and Sir William; they, along with Emma, arrived back in England at the close of 1800. Emma soon after gave birth to her daughter with Nelson – Horatia, shown here in a portrait that resembles the depiction of her mother by Vigée Le Brun.

Emma and Nelson created a house to celebrate their love in Merton Place, south-west London. Sir William grew increasingly weary of the frantic pace of life in London and died in 1803. The relationship between the three is satirised in James Gillray's (1756–1815) print Dido, in Despair! (1801), in which Emma is cruelly depicted as overweight (in fact she was carrying Nelson's child) and is shown in an attitude of despair as Nelson's fleet sets sail, a frail Sir William asleep in the background.

Nelson died at the Battle of Trafalgar in 1805, after being shot by a French sniper. In the years after, Emma tried and failed to get a pension from the government. In 1814, she fled to Calais with Horatia, in extreme poverty, dying in January 1815, aged 49, without seeing the end of the Napoleonic wars which had shaped her life.

She had risen high, becoming one of the most famous women in the world, and after her death, she was condemned by a new Victorian age that had no compassion for a woman who had been a mistress. Merton Place was destroyed and her belongings were sold.