Now, nearly half a century after the court case that made him the world's best-known prisoner of conscience, a new book claims that whatever the wider injustice perpetrated, the apartheid-era prosecutors were indeed right on one question: Mr Mandela was a Communist party member after all.
The former South African president, who won the Nobel Peace Prize in 1993, has always denied being a member of the South African branch of the movement, which mounted an armed campaign of guerrilla resistance along with the ANC.
But research by a British historian, Professor Stephen Ellis, has unearthed fresh evidence that during his early years as an activist, Mr Mandela did hold senior rank in the South African Communist Party, or SACP. He says Mr Mandela joined the SACP to enlist the help of the Communist superpowers for the ANC's campaign of armed resistance to white rule.
His book also provides fresh detail on how the ANC's military wing had bomb-making lessons from the IRA, and intelligence training from the East German Stasi, which it used to carry out brutal interrogations of suspected "spies" at secret prison camps.
As evidence of Mr Mandela's Communist party membership, Prof Ellis cites minutes from a secret 1982 SACP meeting, discovered in a collection of private papers at the University of Cape Town, in which a veteran former party member, the late John Pule Motshabi, talks about how Mr Mandela was a party member some two decades before.
