The cancer which killed the man convicted of the Lockerbie bombing was a "gift from God" to establishments with something to hide, according to the Libyan's biographer.
John Ashton made the claim at the Edinburgh International Book Festival, joined by other high-profile critics of the controversial case.
Jim Swire, who lost his daughter in the 1988 bombing of Pan Am flight 103, and Hans Kochler, the UN observer at the subsequent trial in the Netherlands, also took part before a capacity crowd.
Abdelbaset al-Megrahi was sentenced to life for the atrocity which claimed 270 lives above Lockerbie and on the ground at the town. He was released from prison on compassionate grounds after being diagnosed with prostate cancer, which eventually led to his death in May.
Mr Ashton, who recently published a book on the former Libyan intelligence officer, said: "Megrahi's cancer was a gift from God for everybody involved that had something to hide. It allowed his release, it allowed the final stages of the rapprochement between the UK and Libya, and it allowed the Scottish Government to allow him out of prison on a legal basis that wasn't one laid down by the hated government in Westminster. It was a tragedy for Megrahi but I think everybody else was punching the air."
The course of events was a "political fix", he told the audience at the venue in Charlotte Square. But he denied the trial was a "grand conspiracy" involving a range of security services and leading all the way to heads of state such as the US president. "What I say is, first and foremost, that the judges got it wrong, for whatever reason, and the Crown Office withheld evidence," he said. "I'm sure they did so in good faith but their behaviour was utterly incompetent and shameful."
The three men highlighted areas of evidence, heard under Scots law at Camp Zeist in Utrecht, which they said undermine the case against Megrahi. Key among them was a break-in at Heathrow Airport and discrepancies over the identification of Megrahi in a shop in Malta.
Dr Kochler said he cannot understand why Megrahi was found guilty but his alleged co-conspirator was not. "If such an argument, if such an opinion of court, was presented by a student in a seminar, he would not have passed because it is full of contradictions," he said. "They got it wrong. But the question is why?" He said the trial was politically motivated.
Mr Swire, an outspoken critic of the trial, believes a bomb was taken on board at London. "During the whole trial we did not know that Heathrow Airport had been broken into 16 hours before Lockerbie happened, it seemed to me very likely that was the technology that had been used," he said. "The whole concept that the thing came from Malta via Megrahi's luggage or anyone else's seemed to me far-fetched."
The panel's comments underlined the gulf between those who believe in Megrahi's guilt and those who feel he was innocent or the victim of a miscarriage of justice. American relatives in particular were angered by Scottish Justice Secretary Kenny MacAskill's decision to free Megrahi under compassionate release rules.