TAM DALYELL, the former campaigning MP who died on Thursday, said in a poignant final interview he would go to his grave believing that the conviction of the alleged Lockerbie bomber Abdelbaset al-Megrahi was a “massive injustice.”

He recalled that after visiting Megrahi in prison, “I was absolutely convinced that he was not involved in Lockerbie.”

Two hundred and seventy people died when Pan Am flight 103 exploded over Lockerbie on December 21, 1988. Megrahi, who died in 2012, was the only person convicted of the attack.

The ex-Linlithgow MP, who inherited the Baronetcy of the Binns in 1972, spurned his title and was never known as Sir Tam. His interest in the Lockerbie case began 10 days after the bombing when he was approached by a police whistleblower who complained that American agents were wandering the crash site without police supervision.

The officer, a constituent, was among hundreds of Lothian and Borders police sent to Lockerbie the day after the crash to help the local Dumfries and Galloway force.

In his last interview Dalyell recalled, “[The officer] said he was very uncomfortable because Americans were allowed to go around where they liked in a way that would not be acceptable in any Scottish murder investigation and the normal police rules were absolutely being thrown to the wind.”

He said the officer had never wavered from his claims and had last repeated them only two years ago, but did not wish to go public. “I think this is partly about pensions and police etiquette, but he sticks absolutely to his story,” Dalyell said.

There are longstanding claims that large quantities of drug and cash were removed by Americans agents from the crash site. The agents were also said to be concerned about items belonging to a US intelligence team who died on Pan Am 103 while returning from an aborted hostage rescue mission in Lebanon.

Some of Megrahi’s supporters suspect that American intelligence agents manipulated evidence in order to frame Megrahi and conceal the truth about the bombing. Initial indications suggested that the bombing had been commissioned by the Iranian government and carried out by a Syrian-based group the Popular Front for the Liberation of Palestine – General Command (PFLP-GC).

Two months before Lockerbie the German police caught members of the group with a bomb designed to detonate at altitude, built in to a Toshiba radio-cassette player. Forensic evidence suggested that the Lockerbie bomb was also contained within a Toshiba radio-cassette player, although a different model.

Three months after the bombing the UK government’s transport secretary Paul Channon privately briefed lobby journalists that the PFLP-GC was behind the attack He later lost his job after being named as the source of the story. Dalyell, who was a close friend, revealed that Channon was angry at his treatment by the government.

Many were surprised when, in 1991, the then Lord Advocate, Lord Fraser of Carmyllie, and US Department of justice announced charges against Megrahi and another Libyan, Lamin Khalifa Fhimah. The UK and US governments both made clear that Iran and the PFLP-GC had been exonerated.

Dalyell condemned Fraser as being a “quite unsatisfactory Lord Advocate [who] just went along with the Crown Office line.” He added, “[He] was absolutely beholden to Mrs Thatcher because he had lost a blue chip seat in Angus so had no job and was made a law officer by the generosity of the Prime Minister.”

During the nineties Dalyell frequently urged the Conservative government to agree to Libyan proposals to try the two suspects before a Scottish court in a neutral venue. He also tabled numerous parliamentary questions about events at the crash site and other facts that challenged the official narrative. He initiated sixteen adjournment debates on Lockerbie, which he said was four times as many as anyone had ever had on a single subject.

In 1997 the new Labour government signaled that it was prepared to accept a neutral venue trial and in 2000 Megrahi and Fhimah were tried before three law lords at a specially-convened Scottish court at Kamp Zeist in The Netherlands. Fhimah was acquitted and Megrahi was found guilty and sentenced to life in prison with a minimum 20-year tariff, later increased to 27 years.

Dalyell believed the guilty verdict was built on unreliable evidence and flawed reasoning. The judges accepted the prosecution claim that two weeks before the bombing Megrahi bought the clothes that were later packed in a suitcase with the bomb from Maltese shopkeeper Tony Gauci. However, evidence suggested that the clothes were bought when Megrahi was not in Malta and Gauci described the purchaser as being considerable older and larger than Megrahi.

Visits to Megrahi in Barlinnie and Greenock prisons convinced him that the Libyan was innocent. “With 43 years in the House of Commons one develops an instinct as to whether one is being told the truth or spun a yarn,” he recalled, “My whole body reacted to the fact that I was being told the truth.”

Following a failed first appeal, in 2007 the Scottish Criminal Cases Review Commission granted Megrahi a second appeal on six grounds including flawed reasoning by the trial court judges. In 2009, following a diagnosis of terminal cancer, Megrahi abandoned the second appeal in the belief that it would aid an application to Scottish justice secretary Kenny MacAskill for compassionate release. MacAskill controversially granted the application a few days later and Megrahi was allowed to return to Libya, where he died three years later.