Tony Blair failed in his attempts to stop Nelson Mandela raising the Lockerbie bombing at a Commonwealth Heads of Government meeting (CHOGM) in Scotland, despite being warned by aides the South African leader’s intervention over the terror attack would be “pretty disastrous”, new files show.

Downing Street officials warned the then-prime minister ahead of the 1997 summit in Edinburgh that Mr Mandela was visiting Libya, which later admitted responsibility for the airliner disaster, before heading to CHOGM, and urged Mr Blair to speak to him.

But Mr Blair’s efforts – including a personal letter to Mr Mandela a week before the CHOGM, urging him to “avoid a discussion” about Lockerbie – failed, and the enduring controversy over a failure to bring any perpetrators to justice ended up being one of the key themes of the leaders’ summit.

A tranche of previously classified files released by the National Archives at Kew shows a handwritten note from Downing Street aides urging Mr Blair “to speak to” his South African counterpart.

Mr Blair duly wrote to Mr Mandela, explaining the complexities of bringing suspects to justice, having resisted calls to hold a trial in a different country.

Mr Blair wrote: “Lockerbie is of course a particularly sensitive subject in Scotland because of the deaths on the ground of 11 inhabitants of the small town of Lockerbie, in addition to the 259 people on board the aircraft.

“So I hope we can avoid a discussion of the issue at CHOGM itself – we have a lot of other things to talk about.

“But I would welcome a further private discussion when we meet next week.”

The letter ended with the handwritten sign-off: “Very best wishes. Yours ever, Tony.”

Mr Blair’s hopes were in vain when Mr Mandela was asked about the subject, claiming justice would not be seen to be done if any trial was held in Scotland itself.

He said: “I have never thought that in dealing with this question it is correct for any particular country to be the complainant, the prosecutor and the judge.

“Justice, it has been said especially in this country, should not only be done but should be seen to be done.

“I have grave concern about a demand where one country will be all these things at the same time. Justice cannot be seen to be done in that situation.”

The move, however, provided an unlikely fillip for Mr Blair – as his subsequent invitation to meeting grieving families at Downing Street was seen as an intention to listen after years of refusal.

Pan Am flight 103 was travelling from London to New York on December 21 1988 when it crashed in Lockerbie and killed 270 people.

It was Britain’s largest terrorist atrocity.

Former Libyan intelligence officer Abdelbaset al-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 ever convicted of the attack.

He was released from prison in 2009 on compassionate grounds having been diagnosed with prostate cancer and returned to Libya to a “hero’s welcome”.

He died in Tripoli in 2012, aged 60.