Mystery still surrounds al-Megrahi, the spy on FBI's most wanted list

This week's decision by al-Megrahi to abandon his appeal against conviction means the mystery over his exact role may never be solved.

Lockerbie victims' relatives were desperate to use the process to get answers to questions that have dogged the case since the Libyan was jailed.

An intelligence officer for Muammar Gaddafi, he was on the FBI's top 10 "most wanted" list for 10 years and some say the case against him is strong.

As chief of security for Libyan Arab Airlines, he had access to the airline's office in Malta. From there, the prosecution said al-Megrahi was able to use up to four false passports to travel to Zurich, where the timing device for the bomb was made, and Tripoli. Several months after the attack, police found a fragment of the bomb timer in a piece of clothing in a Scottish forest.

The labels led investigators to a shop in Malta. Tony Gauci, a Maltese shopkeeper, was the only man to identify al-Megrahi. He picked out the Libyan at an identity parade as having bought the clothes. But prosecutors failed to tell the defence that shortly before this, Mr Gauci had seen a magazine article with a picture of al-Megrahi.

Dr Jim Swire, whose daughter Flora was a victim, said a break-in the night before the attack near the Pan Am baggage area at Heathrow was not fully investigated. Secret documents before the appeal court might have provided new information but they remain unpublished due to security fears.