It amounts to an acknowledgement that the UN sanctions against Libya imposed in 1992 when Colonel Gaddafi refused to hand over the two men, were never going to work.
The UN Security council will this week be asked to approve the new deal offered yesterday to have them face trial in the Netherlands before a specially located Scottish court and the British Government will endorse the plan in council.
One crucial factor behind the U-turn lies the fact that Mr Cook, who has a Scottish constituency, had come under sustained pressure from the PanAm 103 families since taking office for a shift in the stance inherited from the Tories, to allow the trial to take place in a neutral country, as the Libyans had suggested.
London and Washington had been holding out for a trial in Scotland in the hope that the Libyan leader would be brought to heel by the sanctions
But the Foreign Secretary privately told Lord Hardie it was not likely that Colonel Gaddafi would hand over the suspects for trial in Scotland.
Lord Hardie's review of the evidence concluded, like his Tory predecessors', that there was enough evidence to justify prosecution, but accepted Mr Cook's judgement that sanctions were never going to work.
Tony Blair raised the prospect of a trial in The Hague or Amsterdam with Bill Clinton, the US President, but it was not until July that the Dutch authorities agreed to the deal.
There were still loose ends. Questions over whether there should be international judges headed by a Scottish judge, as the Libyans wanted, had to be ironed out. So too had the legal complexities - the accused will be held by Scottish prison officers in The Hague under Scottish legal jurisdiction.
Mr Cook had hoped to make a statement to the Commons in July, before MPs broke up for their recess, but the Dutch Cabinet was unable to approve arrangements until yesterday.
If the trial eventually took place, it could last up to a year, cost more than pounds 10 million and would probably fail to convict.
Professor Mike McConville, head of Warwick University's law school and one of the country's leading legal experts, said: "The prosecution task is not impossible but it is still going to be formidable. The evidence would have to be extremely persuasive and it would have to be stronger than the material which has so far come into the public domain if there were to be convictions."Reuse content