The news comes on the eve of publication of a book by Peter Hain, the Labour MP for Neath, who as a 15-year-old made a speech at the funeral of John Harris, hanged after Mr Lloyd gave evidence against him.
Mr Lloyd, 54, a barrister, was a member of the African Resistance Movement with Mr Harris. They carried out sabotage and had a policy of not endangering life, but Mr Harris planted a bomb in Johannesburg station which killed an elderly woman.
Mr Hain's book, Sing the Beloved Country, claims that a message was smuggled into Mr Lloyd in jail to say that if he gave evidence Mr Harris would be sentenced to death.
"However, Lloyd ignored this warning," he writes. "At the trial he did not merely give evidence in corroboration of John's own confession (which would have carried a life sentence for manslaughter), but went further. He insisted that John had said that it would be tactically advisable for a few lives to be taken because it would save many lives in the future. John consistently denied this."
Lloyd was released in exchange for turning state witness and fled to Britain. There he was asked by an associate of Mr Harris to retract crucial evidence but refused, threatening to tell the South African Security Police that she was trying to get him to perjure himself, the book states.
"So another approach was tried. Ruth Hayman, John Harris' lawyer... also well known to him, flew over. At great professional and personal risk she approached Lloyd who agreed to a draft affidavit retracting his evidence and left promising to return in the morning to sign it. But he failed to do so."
Mr Lloyd declined to comment yesterday.
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