Sir Jeremy Greenstock is a trim, smart and fiercely intelligent man: a diplomat of the old school. On 9 March last year, with war in Iraq less than a fortnight away, the then UK ambassador to the UN was sitting in his New York office on a Sunday afternoon waiting for Lamine Sidime, Prime Minister of the tiny African state of Guinea.
From the British government's point of view it was to be a crucial meeting.
With the war drums beating ever louder in Washington, Britain - with Greenstock out in front - was still pushing for a second UN resolution that would authorize a war against Iraq but give Saddam one last chance to avoid a conflict.
And at the center of the negotiations were six countries - non-permanent members on the Security Council - on whose support the vote depended.
Guinea was one of the six. Then there were Angola, Cameroon and Pakistan. Crucially the number would be made up by Mexico and Chile.
Even as Sidime sat down on the sofa in Greenstock's office, the members of the Middle Six, as they were known, were aware of how high the stakes were.
Not only had they found themselves the subject of a diplomatic bombardment by the US and the UK in search of their votes, but a week before they had been made brutally aware of how tough Britain and America were prepared to play.
On 2 March a leaked document from Britain's secret listening center, GCHQ - published in this paper - had disclosed that both countries were involved in an intelligence operation to calculate the voting intentions of the six over a second compromise resolution.
As it would turn out, calculations other than securing UN legitimacy for any war were secretly in play.
For while Greenstock and his masters at the Foreign Office and Downing Street were desperately working to secure a resolution that would ensure clear international legitimacy for any attack on Iraq, Washington, as it now increasingly appears clear, regarded even Britain's diplomatic efforts as a hurdle on its road to war.
The extraordinary story of the diplomacy of those two weeks - which saw the abandonment of any attempt to secure that elusive second resolution, as The Observer can now reveal - was also the story of an intelligence operation that, at every step, attempted to undermine the independent deliberations of the Security Council as it stood on the brink of war.
It would be the spies, not the diplomats, who would carry the day.
For even as Middle Six diplomats sat down in private to draw up a resolution that bridged the gap between France, Germany and Russia on the anti-war side, and the US and UK - a compromise that would set a final deadline to Saddam and delay the outbreak of war - someone was listening in and anticipating their every step.
Adolfo Aguilar Zinser, Mexico's representative to the UN, could hardly be more different from Greenstock. A maverick politician, with a background in left-wing academia, he had been a key figure in helping win the support of the Left for President Vicente Fox in the 2000 elections. And while Greenstock is a figure of calculated Foreign Office discretion, Aguilar Zinser is a man who last week threw diplomatic caution to the wind to expose the full details of the US-led spying on the Middle Six.
On Friday Aguilar Zinser gave his fullest version of what he believed was happening in the UN in that fortnight, and in a crucial meeting that history may decide made war against Iraq inevitable.
Aguilar Zinser is still careful in some respects. He says six countries attended that meeting, but will not say who, although it is certain that it was members of the Middle Six. He will also not say where they met. What he is absolutely certain of is that the US was bugging the meeting. As the representatives to the UN sat down at their meeting it was to work on a 'draft document' of a compromise resolution.
'We had yet to get our capitals to go along with it, it was at a very early stage ... only the people in the room knew what the document said,' said Aguilar Zinser last week. 'The surprising thing was the very rapid flow of information to the US quarters. When they [the US] found out, they said you should know that we don't like the idea and we don't like you to promote it.
'The meeting was in the evening. They call us in the morning before the meeting of the Security Council and they say: "We appreciate you trying to find ideas, but this is not a good idea." I say: "Thanks, that's good to know." We were looking for a compromise and they say, "Do not attempt it."
'It was very obvious to the countries involved in the discussion on Iraq that we were being observed and that our communications were probably being tapped. The information was being gathered to benefit the United States.'
Chile had other reasons to believe they were being targeted by a US intelligence operation. On Tuesday, following last week's Observer disclosure that GCHQ had participated in the intelligence operation against the UN, Chile charged publicly for the first time that its UN mission telephones were tapped as the Security Council considered a resolution authorizing war against Saddam Hussein.
A Chilean government spokesman refused to say who was suspected of tapping the telephones but said government officials 'expressed our concern to the respective institutions'.
The significance of Mexican and Chilean revelations last week go beyond the acknowledgment of what many diplomats in the UN suspect: that they are often targeted by the US in breach of the Vienna conventions.
They build on the revelations of GCHQ whistleblower Katharine Gun, facing trial for breaking the Official Secrets Act in leaking details of espionage against the Middle Six, and could lead to a re-writing of the history of the build-up to the war against Iraq.
In precis, the official version of those desperate final weeks has it like this: after bruising negotiations between London and Washington, Tony Blair and Jack Straw secure a last moment for diplomacy from Washington to secure a second resolution.
Washington concedes; the Middle Six fail to come up with an acceptable conclusion; and France kills any chance of agreement when Chirac says he will not back war in any circumstances.
What the new revelations suggest is that despite the US agreeing to more time to find a resolution, it secretly used intelligence from spying on those negotiations to kill the last hope of a UN resolution.
Most embarrassing of all, it now appears, is that GCHQ participated in a US-led intelligence operation whose conclusion - far from trying to find a new resolution in line with British policy - would undermine our foreign policy on the brink of war.
It is an issue that is unlikely to go away. Mexico and Chile have both now written to Britain and the US demanding an explanation, one that is unlikely to be forthcoming.
The forthcoming Katherine Gun trial will also put the issue back into the spotlight on both sides of the Atlantic, amid a growing campaign that has drawn in Hollywood celebrities.
But it is in Britain that the issue has the potential to be most damaging. For while the Foreign Office continued last week to refuse to discuss the issue, political pressure is now mounting for an explanation of how GCHQ participated in an operation whose end result may have undermined its government's own bid for one last compromise.
© Guardian Newspapers Limited 2004