By . Kieran Corcoran . Scroll down for video . Elegant and charming, an 18th-century painting shows two young, upper-class women who smile daintily on a rural background. These two slender figures, clad in sumptuous clothing and wearing pearls round their necks, would be utterly typical for the period - except for the fact that one of them is black. The mysterious picture seems to show the two women as equal, despite hailing from an era of huge racial prejudice, when Britain still bought and sold Africans in a booming slaving industry. Intriguing: This 1779 portrait, by Johann Zoffany, shows Dido Elizabeth Belle, seemingly the equal of her playmate Lady Elizabeth Murray . And now, rather than being an oddity, it has emerged that Dido Elizabeth Belle - the poised, dark-skinned figure in the portrait - could have played an instrumental part the United Kingdom's historic move to abolish the slave trade for good. Miss Belle, who was taken in by an influential judge and raised almost like one of his family, could have helped sway the mind of her guardian in a landmark series of legal cases which found against avaricious slavers, and helped to end the trade for good. The director of a new film - Belle - depicting her unusual life has spoken of the influence Miss Belle must have had over William Murray, 1st Earl of Mansfield, who looked after her. Legal champion: William Murray, 1st Early of Mansfield, ruled against slavers in a series of rulings . Lord Mansfield, who was Lord Chief Justice (one of the country's most senior judges), took Belle in at the request of his nephew, her father - and went on to make landmark rulings against slave traders, which set the stage for the abolitionist movement. Speaking to the Sunday Telegraph, Amma Asant, the director of Belle, said: 'I think it would be disingenuous to believer her presence in the house didn't have some impact on him. It makes or a fascinating story to think that his love for his child opened his eyes.' The film, which is released in the UK this June, was inspired by the intriguing portrait, which shows Miss Belle posing with her playmate, Lady Elizabeth Murray, a contemporary who was also under Lord Mansfield's care. Miss Belle, born in 1761, was the illegitimate daughter of Lord Mansfield's nephew, John Lindsay, who was a respected captain in the Royal Navy. Her mother is thought to have been an African slave who was captured from a Spanish trip while Mr Lindsay was serving in the West Indies. She was placed into Lord Mansfield's care as a child, and was raised at Kenwood House in Hampstead, North London, where her presence shocked well-to-do visitors. One outraged visitor, a governor of Massachusetts, then a British colony, wrote an astonished diary entry, noting that Lord Mansfield has been 'reproached for shewing a fondness for her.' Big screen: A new film, called Belle, will tell her unusual story. Gugu Mbatha-Raw, pictured above in character, plays Miss Belle . Indeed, Miss Belle was allowed to lead a relatively privileged life - although she did not eat with the family - and married a junior lawyer. Lord Mansfield's will would eventually confirm her freedom. But it was while under his care as a child, and later a young woman, that Lord Mansfield struck two major blows against the slave trade. The first, in 1772, was part of a series of wrangles about the legal status of slavery, which had been tolerated and accepted by courts despite the lack of an actual law to make slave-owning legal. High-class: Miss Belle was raised at Kenwood House in North London, where visitors were shocked at her presence . Lord Mansfield declared that it was in fact illegal for a slave owner to force a reluctant slave to leave the country with him. He said that the fact that slave-master relationships were commonplace was not a good enough reason - and left open the possibility that owners may have no legal rights over their slaves at all. Later, in 1781, he made another ruling which threw out an a claim by slave ship owners who threw men and women overboard to drown, then tried to claim their value back on insurance. But Lord Mansfield ruled that the owners of the Zong - a slave ship travelling from Africa to America - had been wrong to jettison the slaves in the hope of claiming their value back, and described the condition of slavery as 'odious' in his judgment. The case - closely watched by Abolitionist campaigners - helped fuel the movement to end the slave trade, which was eventually outlawed by Parliament in 1807. In 1833 a further law was passed freeing all existing slaves.
Dido Elizabeth Belle was daughter of Royal Navy captain and African slave .
She was raised under care of influential judge in London in 1770s .
Well-to-do guests were shocked to see her arm in arm with white playmate .
Friendship was immortalised in intriguing painting showing them together .
Director of new film telling her story thinks she could have changed history .
Think she may have softened heart of her guardian, the Earl of Mansfield .
Lord Mansfield, the Lord Chief Justice made landmark anti-slaver rulings .
Cases helped fuel the abolition movement - which outlawed slavery in 1833 .
By . Kieran Corcoran . Scroll down for video . Elegant and charming, an 18th-century painting shows two young, upper-class women who smile daintily on a rural background. These two slender figures, clad in sumptuous clothing and wearing pearls round their necks, would be utterly typical for the period - except for the fact that one of them is black. The mysterious picture seems to show the two women as equal, despite hailing from an era of huge racial prejudice, when Britain still bought and sold Africans in a booming slaving industry. Intriguing: This 1779 portrait, by Johann Zoffany, shows Dido Elizabeth Belle, seemingly the equal of her playmate Lady Elizabeth Murray . And now, rather than being an oddity, it has emerged that Dido Elizabeth Belle - the poised, dark-skinned figure in the portrait - could have played an instrumental part the United Kingdom's historic move to abolish the slave trade for good. Miss Belle, who was taken in by an influential judge and raised almost like one of his family, could have helped sway the mind of her guardian in a landmark series of legal cases which found against avaricious slavers, and helped to end the trade for good. The director of a new film - Belle - depicting her unusual life has spoken of the influence Miss Belle must have had over William Murray, 1st Earl of Mansfield, who looked after her. Legal champion: William Murray, 1st Early of Mansfield, ruled against slavers in a series of rulings . Lord Mansfield, who was Lord Chief Justice (one of the country's most senior judges), took Belle in at the request of his nephew, her father - and went on to make landmark rulings against slave traders, which set the stage for the abolitionist movement. Speaking to the Sunday Telegraph, Amma Asant, the director of Belle, said: 'I think it would be disingenuous to believer her presence in the house didn't have some impact on him. It makes or a fascinating story to think that his love for his child opened his eyes.' The film, which is released in the UK this June, was inspired by the intriguing portrait, which shows Miss Belle posing with her playmate, Lady Elizabeth Murray, a contemporary who was also under Lord Mansfield's care. Miss Belle, born in 1761, was the illegitimate daughter of Lord Mansfield's nephew, John Lindsay, who was a respected captain in the Royal Navy. Her mother is thought to have been an African slave who was captured from a Spanish trip while Mr Lindsay was serving in the West Indies. She was placed into Lord Mansfield's care as a child, and was raised at Kenwood House in Hampstead, North London, where her presence shocked well-to-do visitors. One outraged visitor, a governor of Massachusetts, then a British colony, wrote an astonished diary entry, noting that Lord Mansfield has been 'reproached for shewing a fondness for her.' Big screen: A new film, called Belle, will tell her unusual story. Gugu Mbatha-Raw, pictured above in character, plays Miss Belle . Indeed, Miss Belle was allowed to lead a relatively privileged life - although she did not eat with the family - and married a junior lawyer. Lord Mansfield's will would eventually confirm her freedom. But it was while under his care as a child, and later a young woman, that Lord Mansfield struck two major blows against the slave trade. The first, in 1772, was part of a series of wrangles about the legal status of slavery, which had been tolerated and accepted by courts despite the lack of an actual law to make slave-owning legal. High-class: Miss Belle was raised at Kenwood House in North London, where visitors were shocked at her presence . Lord Mansfield declared that it was in fact illegal for a slave owner to force a reluctant slave to leave the country with him. He said that the fact that slave-master relationships were commonplace was not a good enough reason - and left open the possibility that owners may have no legal rights over their slaves at all. Later, in 1781, he made another ruling which threw out an a claim by slave ship owners who threw men and women overboard to drown, then tried to claim their value back on insurance. But Lord Mansfield ruled that the owners of the Zong - a slave ship travelling from Africa to America - had been wrong to jettison the slaves in the hope of claiming their value back, and described the condition of slavery as 'odious' in his judgment. The case - closely watched by Abolitionist campaigners - helped fuel the movement to end the slave trade, which was eventually outlawed by Parliament in 1807. In 1833 a further law was passed freeing all existing slaves.
oddity, it has emerged that Dido Elizabeth Belle - could have played an instrumental part the in by an influential judge and raised almost like mind of her guardian in a landmark series of The director of a new film - Belle - depicting Lord Mansfield, who was Lord Chief Justice (one Miss Belle posing with her playmate, Lady under Lord Mansfield's care. Miss Belle, born in 1761, was the illegitimate daughter of Lord respected captain in the Royal Navy. Her mother is thought to have been an African slave who was Belle was raised at Kenwood House in North London, where visitors were shocked at her watched by Abolitionist campaigners - helped fuel the movement to end the slave trade, which was