£100,000 call to save freed slave's portrait

The National Portrait Gallery needs to raise 100,000 to secure the

portrait of African Muslim Ayuba Suleiman Diallo.

The "national treasure" has not been displayed before in public but has gone on show temporarily at the London gallery to help raise support.

High-profile backers of the appeal include writer Bonnie Greer and broadcaster Zeinab Badawi, playwright and former Casualty star Kwame Kwei-Armah, artist Faisal Abdu'Allah and Kids Company founder Dame Camila Batmanghelidjh.

Greer said in a statement: "The most moving thing of all, more important than even the story of this heroic and influential man, is that Ayuba Sulieman Diallo's face is the face of contemporary Britain.

"Go out into our major cities and you will see him all around you – male and female.

She added: "Therefore this portrait is at once an important historical artefact and a major contemporary work."

The sitter, who was known in Britain as Job ben Solomon, is shown in his traditional dress with a copy of the Koran around his neck.

The portrait, from a private collection, was sold at Christie's auction house in December and has been placed under a temporary export bar. The gallery needs to raise 554,937.50 by August 25.