A painting by one of South Africa's leading artists, auctioned to help fund Nelson Mandela's legal defence in the 1960s, has been rediscovered at a flat in London and valued at $1.5m (£1m).
An art expert spotted Arab in Black, by Irma Stern, being used as a kitchen notice board in the UK capital.
The work was sold for charity to raise funds for Mr Mandela and other anti-apartheid activists in their treason trial, which ran from 1956 until 1961.
It is due to be auctioned in September.
"I spotted this masterpiece hanging in the kitchen covered in letters, postcards and bills," said Hannah O'Leary, a specialist in South African art at Bonhams auction house in London.
"It was a hugely exciting find even before I learned of its political significance."
It is thought that the current owner was given the painting by their parents, and brought it to the UK in the 1970s.
Mr Mandela and the other defendants were found not guilty in 1961 - but three years later he was sentenced to life in prison for committing acts of sabotage.
He spent 27 years in jail before becoming South Africa's first black, democratically elected president in 1994 - ending years of white-minority rule.
Ms Stern died in 1966, and her home in Cape Town has been converted into a museum.