By Paul Reynolds
World affairs correspondent, BBC News
Jack Straw points out that the transfer deal was "academic" for Megrahi (left)
More and more is now emerging about the efforts made by the British government to secure the transfer to Libya of Abdelbaset Ali al-Megrahi.
On 24 August, I pointed out that, although the decision to release Megrahi had been taken by the Scottish government on compassionate grounds (that government being in charge of judicial affairs in Scotland), there had been
an earlier plan
by London to get the prisoner back to Libya in another way - by using a prisoner transfer agreement with Libya.
I said: "British ministers and diplomats have a lot of explaining to do yet."
Evidence of the plan could be seen at that time in a leaked letter from a Foreign Office minister, Ivan Lewis, to the Scottish justice secretary, Kenny MacAskill.
Mr Lewis said: "I hope... you will now feel able to consider the Libyan application in accordance with the provisions of the prisoner transfer agreement."
Part of the explaining has now come to pass, not because the British government has suddenly revealed all, but because of more leaked government letters, published by the Sunday Times.
This shows the extent of the British government's proposal.
It is ironic perhaps that a Scottish nationalist government came to the rescue of a British government
On 26 July 2007, the British justice secretary, Jack Straw, wrote to Mr MacAskill saying that he agreed that Megrahi should not be included in a prisoner exchange agreement then being negotiated with Libya. The device proposed was to make prisoners eligible only after a certain date.
However, on 19 December 2007, Mr Straw changed his mind. "In view of the overwhelming interests of the United Kingdom," he wrote, Megrahi would now not be excluded.
Mr Straw himself has had to take a break from the holiday weekend in the UK to appear in front of the TV cameras to defend his decisions.
He admitted that Libya had insisted on a standard prisoner exchange deal, not excluding anyone, of a type negotiated by the UK with many other countries.
it is quite convenient from their point of view for the Libyans to argue that an understanding had been reached with the UK as it strengthens their standing domestically and abroad as a government able to get their prisoner back home
Mr Straw strongly denied however that his change of mind was connected to a commercial agreement that BP was trying to arrange with Libya over oil exploration.
Libya had blocked this while the prisoner transfer talks were going on, yet as soon as the transfer agreement was settled, obstacles in the way of the BP deal were suddenly removed.
"There was no deal," Mr Straw said. He further justified his position by pointing out that the Scottish government had the final word on any release, whether by transfer or on compassionate grounds.
In the event, of course, the Scottish decision to release Megrahi was taken on the compassionate ground that Mr MacAskill has explained - Megrahi is terminally ill with cancer.
Plan A not used
Megrahi had played his own part by withdrawing his appeal against conviction. Any appeal holds up a transfer. As it happens there is also an outstanding appeal by the Scottish authorities against sentence and that would have had to have been settled first.
But time was running out, with the cancer said to be reaching a critical stage.
Megrahi (left) has backed calls for a public inquiry into the bombing
So the British Plan A was never activated. It is ironic perhaps that a Scottish nationalist government came to the rescue of a British government. If Megrahi had died in prison, Libya would no doubt have retaliated against the UK. Perhaps there would have not been a BP agreement.
In the meantime it is quite convenient from their point of view for the Libyans to argue that an understanding had been reached with the UK as it strengthens their standing domestically and abroad as a government able to get their prisoner back home.
The background to all this is that the US and UK have made great efforts to bring Libya in from the diplomatic and commercial cold over recent years.
Libya first agreed to pay compensation for Lockerbie and to hand over Megrahi and another suspect (who was acquitted).
Then, in December 2003, Libya agreed to end a covert nuclear weapons programme it had been caught red-handed by the Americans and British trying to develop.
The result has been a new era in relations - and a rush to exploit Libya's oil and commercial potential. Paul.Reynolds-INTERNET@bbc.co.uk