Face of the greatest black Briton is finally discovered... at car boot sale

Her selfless acts of charity tending to dying soldiers in the bloody battlefields of the Crimea earned her the belated but esteemed title of the nation's greatest black Briton.

But despite the posthumous recognition of the West Indian-born nurse Mary Seacole last year, her public profile has remained stubbornly low compared to that of her more famous white counterpart Florence Nightingale.

Yesterday, it appeared that this was destined to change as the only known painting of the Crimean War heroine went on display at the National Portrait Gallery in London for the first time.

The oil painting, which was found on the back of another print, was sold at a car boot sale in the Cotswold town of Burford before it was auctioned to a dealer at a social club in Shipston on Stour, Warwickshire.

It was at this stage that its new owner, curious to confirm the identity of the elderly black lady in the painting, realised its significance. Checks on the bemedalled sitter suggested she was Mary Seacole.

Helen Rappaport, who has been researching Seacole for the past three years, confirmed that the painting matched existing images of the nurse, such as a bust from 1871 and a photograph. She promptly bought the painting and yesterday she presented it on long-term loan for display at the National Portrait Gallery.

The Jamaican-born nurse set up her own nursing and supplies business in the Crimea after being rejected for formal duties by the British War Office, almost certainly because of her race.

Ms Rappaport said she was delighted that the portrait would be on public view. "As an admirer of Mary Seacole's courage and humanitarianism, I am extremely happy that she can at last take her rightful place in British history as an important female personality of the Crimean War," she said.

The portrait was painted in 1869 by Albert Charles Challen, who died aged 34, only a few months after Seacole died in 1881 at the age of 76. It shows a dignified figure, proudly bearing the red neckerchief of her Jamaican Creole origins as well as the three medals she was awarded for her service: the British Crimean medal, the Turkish Medjidie and the French Legion of Honour.

"I find it amazing that, unknowingly, [Challen] has painted a defining image of one of the most important black women in British history," Ms Rappaport said.

At some point, however, the painting was turned face in to back another print, a move that saved it from damage, although it could easily have led to its destruction.

Ms Rappaport said: "By a miracle it survived. Finding something like this you could define as every writer/researcher/historian's wildest dream ... I knew who the sitter was as soon as I opened the jpeg [computer image]. It was a serendipitous moment, I almost fell off my chair."

Mary Seacole was born in Kingston, Jamaica, in 1805, to a Scottish soldier father and a mother of mixed race who ran a boarding house for invalid soldiers.

When war with Russia broke out in 1854, the patriotic nurse sailed to England to volunteer for the contingent of nurses being recruited by Florence Nightingale. The War Office refused to interview her. Undeterred, she made her own way to the Crimea.

When Florence Nightingale also personally refused to accept her offer of services, Seacole opened the British Hotel outside Balaclava. There she combined the role of sutler, or the provider of supplies including alcohol to the troops, with cooking and nursing. Her herbal remedies, particularly for dysentery, were much in demand and her reputation spread through British newspaper columns.

Last year, Seacole received further belated recognition for her work when she topped a poll of the nation's 100 Greatest Black Britons compiled by the website Every Generation.