Here are the key dates relating to the Lockerbie case.
:: December 21 - 270 die as Pan Am flight 103 explodes over the Scottish town of Lockerbie.
:: January 31 - Following a trial at Camp Zeist in the Netherlands, Abdelbaset Ali Mohmed al-Megrahi is found guilty of mass murder and jailed for life.
:: March 14 - Megrahi loses an appeal against his conviction.
:: August 19 - Libya accepts the blame for the Lockerbie bombing and agrees to compensate the victims' families.
:: September 23 - The Scottish Criminal Cases Review Commission (SCCRC) is asked to investigate Megrahi's conviction.
:: March - Prime Minister Tony Blair offers Colonel Muammar Gaddafi “the hand of friendship” following talks with the Libyan leader in a tent outside Tripoli.
:: May - Talks between Mr Blair and Col Gaddafi result in a memorandum of understanding. Negotiations begin on a prisoner transfer agreement (PTA).
An exploration and production sharing agreement between oil giant BP and the Libyan government is signed.
:: June - Scotland's First Minister Alex Salmond raises concerns with Mr Blair that the deal could lead to Megrahi being returned to Libya.
The UK Government agrees to seek a PTA which excludes Megrahi.
The SCCRC recommends that Megrahi is granted a second appeal against his conviction.
:: October-November - Discussions are held between BP and UK Justice Secretary Jack Straw. BP raises concerns about the effect of the slow progress of the PTA negotiations on commercial interests, including the ratification of the BP exploration agreement.
:: December 19 - Mr Straw writes to his Scottish counterpart, Kenny MacAskill, to inform him that the UK Government has decided not to exclude Megrahi from the PTA.
:: January - The BP exploration deal is ratified by the Libyan government.
:: September - Megrahi is diagnosed with terminal prostate cancer.
:: November - The PTA is signed.
:: April 29 - The PTA comes into force, allowing Megrahi to apply to serve the rest of his sentence in a Libyan jail. He must drop his appeal against his conviction for any PTA to take place.
:: May 5 - The Libyan government submits a formal application to the Scottish Government for Megrahi's transfer under the PTA.
:: July 24 - The Libyan government submits an application to the Scottish Government for Megrahi's release on compassionate grounds.
:: August 9 - In a communication to the Scottish Government, US authorities say a conditional release on compassionate grounds is a “far preferable alternative” to Megrahi's transfer back to a Libyan jail.
:: August 14 - US secretary of state Hillary Clinton urges Mr MacAskill not to release Megrahi.
:: August 18 - Megrahi's bid to drop his second appeal against his conviction is accepted by judges in Edinburgh.
:: August 20 - Having rejected Libya's application under the PTA, Mr MacAskill announces his decision that Megrahi is to be returned to his home country on compassionate grounds.
:: August 21 - The UK and the US condemn the “hero's welcome” given to Megrahi as he arrives in Tripoli to cheering crowds.
:: August 22 - Libyan television shows pictures of Col Gaddafi meeting Megrahi and praising Prime Minister Gordon Brown and the UK Government for their part in securing his freedom.
Mr Brown says later he is “repulsed” by Megrahi's welcome in Libya and insists the British government had no role in the decision to free him.
:: September 2 - The Scottish Government suffers a defeat in Parliament over its handling of the Lockerbie case.
:: September 5 - Mr Straw acknowledges that the prospect of trade and oil deals with Libya played “a very big part” in his decision to include Megrahi in the PTA.
:: September 26 - Col Gaddafi said no deal was done to secure the release of the man convicted of the Lockerbie bombing.
:: July 15 - Mrs Clinton says she will look into claims by a group of senators that BP lobbied the Government to release Megrahi in order to smooth an oil deal with Libya.
:: July 20 - On his first visit to Washington as Prime Minister, David Cameron tells US media that Megrahi should have died in jail. He asks Cabinet Secretary Sir Gus O'Donnell to review the Government's documentation on his release.
:: July 22 - The Scottish Government declines a request from US senators that Mr MacAskill appear at a hearing of the Foreign Relations Committee on the Lockerbie controversy. Mr Straw declines the same request the following day.
:: July 29 - Senator Robert Menendez says the committee will send members to the UK to question witnesses.
:: August 20 - On the first anniversary of Megrahi's release, US senators say a “cloud of suspicion” remains over the decision to return him to Libya and call for an inquiry.
:: September 16 - Scottish justice officials hold a meeting with an American delegation investigating Megrahi's release.
:: September 29 - The Senate Foreign Relations Committee hears that a review of US government records found no information about BP attempting to influence the release of the Lockerbie bomber.
:: October 19 - More than 1,200 people back an independent inquiry into Megrahi's conviction in a petition lodged at the Scottish Parliament.
:: December 9 - There are claims that the Lockerbie bomber is close to death after a rapid deterioration in his health.
:: January 31 - A diplomatic cable obtained by the WikiLeaks website shows that advice was given to Libya by a British government minister on how to secure Megrahi's release.
:: February - Sir Gus announces that the former Labour government did “all it could” to help Libya secure the release of the Lockerbie bomber.
:: February 23 - Libya's former justice minister, Mustafa Abdel-Jalil, who stepped down in protest against anti-government demonstrations, tells Swedish newspaper Expressen he has proof that Col Gaddafi ordered the Lockerbie bombing.
:: March 31 - Libyan foreign minister Musa Kusa apparently defects to Britain, saying he is “no longer willing” to represent the dictator. Scottish prosecutors say they want to interview him in connection with the the Lockerbie case.
:: April 8 - Police investigating the Lockerbie bombing meet Musa Kusa.
:: May 6 - The SNP is re-elected in a landslide victory. Mr MacAskill, whose personal share of the vote increased by 13%, said his decision to release Megrahi was not a major issue in the election.
:: May 15 - The Scottish Government announces plans for a change in the law to allow the SCCRC to publish the six grounds upon which it believed Megrahi may have been the victim of a miscarriage of justice.
:: June 28 - The Scottish Parliament's Public Petitions Committee refers a petition by pressure group Justice for Megrahi calling for an independent inquiry into the conviction up to the influential Justice Committee.
:: July 26 - Megrahi appears in a televised pro-government rally in Libya and says his conviction was the result of a “conspiracy”.
:: August 14 - A Libyan government official says Megrahi's cancer has spread to his neck on the day that a poll finds that 48% of UK adults think he should resume his sentence in a Scottish prison.
:: August 19 - The pending second anniversary of Megrahi's release provokes a fresh round of condemnation over the decision.
:: August 20 - The Scottish Government insists it has been “vindicated” two years to the day since the controversial decision to release the Lockerbie bomber from jail on compassionate grounds.
:: August 29 - Megrahi is tracked down to his villa in the Libyan capital where he was apparently comatose and near death. Contact with him had been lost for a time after fighting erupted in Tripoli.
:: September 6 - Megrahi's son says he wants the people of Scotland and the UK to see how ill his father is and allows the BBC into the family's Tripoli home.
:: September 26 - Libyan authorities say they will co-operate with Scottish prosecutors and police investigating the Lockerbie bombing.
:: October 10: Megrahi says “new facts” surrounding the tragedy would be announced in the coming months.
:: October 20: Deposed Libyan leader Muammar Gaddafi is killed by rebels in Sirte.
:: April 13: Megrahi is admitted to hospital for a blood transfusion after his health “deteriorated quickly”.
:: May 20: Reports emerge that the only man convicted of the Lockerbie bombing has died.