A third appeal against the conviction of the late Abdelbaset al-Megrahi for the Lockerbie bombing is due to begin at the High Court in Edinburgh.

The bombing of Pan Am flight 103, travelling from London to New York on December 21 1988, killed 270 people in Britain’s largest terrorist atrocity.

Former Libyan intelligence officer Megrahi, who was found guilty in 2001 of mass murder and jailed for life with a minimum term of 27 years, was the only person convicted of the attack.

An appeal against his conviction was lodged after the Scottish Criminal Cases Review Commission (SCCRC) referred the case to the High Court in March, ruling a possible miscarriage of justice may have occurred.

Judges then granted his son, Ali al-Megrahi, permission to proceed with the appeal in relation to the argument that “no reasonable jury” could have returned the verdict the court did, and on the grounds of non-disclosure of documents by the Crown.

Lawyer Aamer Anwar, who represents the family, said: “It has been a long journey in the pursuit for truth and justice. When Pan Am Flight 103 exploded over Lockerbie nearly 32 years ago, killing 270 people from 21 countries, it remains the worst terrorist atrocity ever committed in the UK.

“Since then the case of Abdelbasset Al-Megrahi, the only man ever convicted of the crime, has been described as the worst miscarriage of justice in British legal history.”

He added: “The reputation of the Scottish criminal justice system has suffered internationally because of widespread doubts about the conviction of Mr Al-Megrahi.

“It is in the interests of justice that these doubts can be addressed; however, he was convicted in a Scottish court of law and that is the only appropriate place for his guilt or innocence to be determined.”

The appeal, which is taking place virtually, begins on Tuesday and will be heard before five judges, including Lord President Lord Carloway.

Megrahi’s first appeal against his conviction was refused by the High Court in 2002 and was referred back five years later following an SCCRC review.

He abandoned this second appeal in 2009, shortly before his release from prison on compassionate grounds while terminally ill with cancer.

He returned to Libya and died in 2012.