The final negotiation took place last week in a private room of the Travellers Club in Pall Mall. The most celebrated past member of the Travellers was Talleyrand, Napoleon’s Foreign Minister, whose name is to diplomacy what Garrick’s is to acting.

Talleyrand said “pas trop de zèle”, but there has been a good deal of zeal in the British diplomacy of the past two years.

I have had the good fortune to know three generations of the Ehrman family. I first met the grandfather, Albert, who retired early from the City to devote his life to his book collection, the Broxbourne Library, of which he published a splendid catalogue. He collected, in particular, the first books printed in many different cities of Europe. The father, John Ehrman, is best known as the author of the classic life of the younger Pitt, itself a magnificent work of scholarship.

William Ehrman I first met in 1977 when he was still third secretary at the embassy in Beijing. He explained the grotesque complexities of the Gang of Four to my wife Gillian and myself, with a complete, if youthful, command of the nuances of Chinese politics. Among his other qualifications for understanding the modern world is his complete fluency in Mandarin.

Perhaps the success of the whole policy should be attributed to heredity. George W. Bush, after all, is the grandson of a distinguished senator, the son of a president and the brother of a governor. Tony Blair’s father was deprived by ill-health of the prospect of a successful career in British politics as that lonely thing, a Conservative in County Durham. There seems to be a meritocracy of genes that works in modern world diplomacy.

Only a couple of weeks ago the success of the post-9/11 American strategy was still in some doubt. One might think that the doubts would prove to be unreal, but they were still being expressed by serious critics. In Britain, the critics included Robin Cook, Kenneth Clarke, as well as Menzies Campbell and the Liberal Democrats. In the United States they included Howard Dean, the frontrunner for the Democratic nomination, and the Democrats generally.

Three events have changed all that: the capture of Saddam Hussein, the Libyan agreement and the much more limited agreement by Iran to allow international nuclear inspectors to make spot checks without warning.

Al-Qaeda had its Pearl Harbor on the ninth of September. It was a sinister and secret attack. The parallel with Pearl Harbor does not consist only of the profound shock to all Americans. When the attack on Pearl Harbor was being planned some of the senior Japanese officers recognised that the only possible outcome would be to awaken an American power that would eventually destroy Japan. Perhaps there were even senior figures in al-Qaeda who had the same premonition. It is always a mistake to attack a power of extreme superiority, particularly the United States.

However, the parallel goes further than that. In 50 years’ time, perhaps earlier, it will be clear to historians that it was Pearl Harbor that was the primary event of the historic reform of East Asia; not just of Japan, but of the whole region. One can easily become confused between economic and political development, between freedom of trade and democracy. They have not always moved at the same speed. China itself has gone fa rther in economic than in political change, though both have moved very far. The American reaction to Pearl Harbor has eventually achieved an open society throughout the greater part of Asia. The example of Japan proved to be a vital part of that process. That is the model for the US response to al-Qaeda, and Iraq is playing the role of Japan in 1945.

The attack on the twin towers is the trigger for a process of liberation in the Islamic world, the penultimate closed society. Only Africa will be left. The United States decided to face the major Islamic countries with a choice between peaceful co-operation and terrorist sympathies.

One by one, the Islamic powers have accepted the conditions of the open global order; the United States has throughout made it clear that force would be used if necessary. The threat of terrorism combined with weapons of mass destruction was too dangerous for the US to tolerate. In this, American policy represented the interest of the whole world, as has been well understood by Russia and China.

After 9/11, Pakistan was the first of the doubtful Islamic nations to make this historic choice; even Turkey hesitated. Afghanistan took a war, but the war was successful. Iraq tried to bluff and to build a coalition of appeasement at the United Nations, with some success. The Americans, rightly backed by Tony Blair, concluded that Saddam Hussein could not be allowed to prevail, that the whole strategy would fall if he survived.

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