Nato ambassadors were given no direct documentation or intercepted communication proving that bin Laden ordered the attacks. As one source put it: "This is not the type of briefing where they come with a copy of a bank transfer or a ticket invoice."
Instead, Taylor reconstructed the events of September 11 and the efforts of the massive FBI investigation to link those who took part in the terrorist attack, through their contacts, to the al Qaeda network and to the Taleban.
He pointed out the areas where more work needed to be done and referred to intelligence reports without going into specifics.
After the classified briefing, the Nato Secretary-General, Lord George Robertson, said: "It is clear that all roads lead to al Qaeda and pinpoint Osama bin Laden as being involved. The facts are clear and compelling.
"The information presented points conclusively to an al Qaeda role in the September 11 attacks.
"We know that the individuals who carried out these attacks were part of the world-wide terrorist network of al Qaeda, headed by Osama bin Laden and his key lieutenants and protected by the Taleban."
Nato invoked the article five mutual defence clause of its 1949 founding treaty for the first time in its history on September 12, but made it conditional on proof that the assault was initiated from abroad.
Robertson said that that "if" had now been removed.
Meanwhile a sombre British Prime Minister, Tony Blair, declared yesterday that the US, Britain and the allies would win against bin Laden's terrorists and their Taleban protectors.
Seeking to prepare the country for war, he said: "Be in no doubt: bin Laden and his people organised this atrocity.
"The Taleban aid and abet him ... They will not stop helping him. I say to the Taleban, surrender the terrorists or surrender power. It's your choice."
Blair added: "This is a battle with only one outcome: our victory, not theirs." He said Britons were "anxious, even a little frightened" about military action, which, he stressed, would not be taken "out of bloodlust".
"Whatever the dangers of action we take, the dangers of inaction are far, far greater. We will do all we humanly can to avoid civilian casualties."
He pledged that the Taleban's military hardware would be eliminated, its finances cut off, its supplies disrupted and its troops targeted.
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