Lockerbie bombing, Iranian not Libyan plot.

A documentary claims to have uncovered fresh evidence that Iran, not Libya, ordered the bombing of Pan Am flight 103 over Lockerbie in December 1988.

The Al Jazeera programme suggests a Palestinian terrorist group retaliated to an American warship shooting down an Iranian civilian airliner.

The only person convicted of the bombing, Libyan intelligence agent Abdelbaset al-Megrahi, died in 2012.

A total of 270 people died when the plane exploded over southern Scotland.

The Al Jazeera programme quotes a "former senior Iranian intelligence official" Abolghasem Mesbahi as saying "Iran decided to retaliate as soon as possible. The decision was made by the whole system in Iran and confirmed by Ayatollah Khomeini."

Five months before the Lockerbie bombing, Iran Air Flight 655 had been shot down by the USS Vincennes, with the deaths of all 290 people on board.

The US government claimed its navy had mistaken the civilian Airbus A300 for an attacking fighter jet.

Tehran vowed that the skies would rain with blood in revenge.

According to Mr Mesbahi, "the target of the Iranian decision-makers was to copy exactly what's happened to the Iranian Airbus. Everything exactly same, minimum 290 people dead."

Al Jazeera claims to have seen US Defence Intelligence Agency cables which reported that the leader of the Popular Front for the Liberation of Palestine General Command (PFLP-GC), Ahmad Jabril, had been paid to plan the bombing.

It quotes a "classified" cable as saying "money was given to Jabril upfront in Damascus for initial expense. The mission was to blow up a Pan-Am flight."

In late December 1988 a terrorist bomb destroyed Pan Am Flight 103 over the Scottish town of Lockerbie and killed 270 people.

Only one man, Abdel Basset al-Megrahi, a Libyan citizen, was tried and found guilty of causing the explosion. But he protested his innocence at the time of his trial in Camp Zeist in Holland in May 2000, and continued to do so up until his death in Tripoli in May 2012.

For three years filmmakers working for Al Jazeera have been investigating the prosecution of al-Megrahi.

Two award-winning documentaries, screened on Al Jazeera in 2011 and 2012, demonstrated that the case against him was deeply flawed and argued that a serious miscarriage of justice may have taken place.

In the first episode, Lockerbie: The Pan Am bomber, we followed defence investigator George Thomson as he revealed how forensic evidence presented at al-Megrahi's trial was not only inaccurate but appears to have been deliberately tampered with.
Then in Lockerbie: Case Closed, we revealed the hitherto secret assessment of the Scottish Criminal Case Review Commission (SCCRC) - an independent public body in Scotland - which had re-examined the case in detail and had recommended that it be referred back to the courts for possible dismissal.

Crucially, our film also showed how new scientific tests comprehensively undermined the validity of the most significant piece of evidence linking the bombing to al-Megrahi and Libya - a fragment of electronic timer found embedded in the shredded remains of a shirt, supposedly bought by the convicted man in Malta.

The timer, the prosecution had claimed, was identical to ones sold to Libyan intelligence by a Swiss manufacturer. But as our investigation proved, it was not identical - a fact that must have been known to British government scientists all along.

Now, in our third and most disturbing investigation, we answer the question left hanging at the end of our last programme: if al-Megrahi was not guilty of the Lockerbie bombing, then who was?

Lockerbie: What Really Happened? will air on Tuesday 11 March at 2000GMT on Al Jazeera English.