LONDON BRIEFING/Chris Johns: "You already know my feeling on Britain and the EU. It will be much better if. . . Britain stays out. The arguments for European unity were once good.

It is only that, for us, the age of chivalry is past. . . our alliance with the British is one of the few substantial and workable liaisons in the world and it will be lost if the British get roped in on the continent. . . I would hope that we might not shove unnecessarily and could rejoice modestly if the British do not make it."

No, this is not a quote from an earlier article of mine. I have never actually advocated British withdrawal from Europe - or even non-participation in the single currency. With one small amendment (EU for EEC), it is a direct quote from a letter sent by Prof JK Galbraith, one of the leading economic policy advisers of the time, to the then US President, John F. Kennedy.

The letter reveals much about US attitudes towards Europe, attitudes that are unlikely to have changed very much over the past four decades. Current circumstances and much that has occurred in recent years echo the underlying thrust of Prof Galbraith's argument.

There is a special relationship between the US and Britain, despite the scoffing of the sceptics.

It may be unequal, it may not run very deep but, then and now, the US regarded Britain as its only friend of any real substance, of any real durability.

Many people in Britain have been genuinely puzzled by Prime Minister Tony Blair's stance on Iraq. A proper understanding of history - which Mr Blair possesses - puts it into context.

Mr Blair has been operating on two levels. First, the special relationship must be maintained, not just for its own sake but, simply, because the alternative is too awful to contemplate. The neo-conservatives (neocons) in Washington couldn't care less about being friendless. This was fine for as long as the US stayed true to its isolationalist instincts. But, as Mr Blair has said many times, September 11th changed everything - and few people have yet to realise by just how much they have changed.

Mr Blair has decided to remain the best friend of the US in the hope that he can continue to restrain the wilder excesses of the neocons.

One of them was quoted recently as saying: "We all want to go to Baghdad, real men want to go to Tehran."

Although ultimately a dismal failure, the attempt to go through the UN was Mr Blair's idea, so he does wield some influence. And he does have big ideas for the post-Iraq world order.

The key way that September 11th changed US attitudes was to destroy the cosy consensus that any country can do what it likes within its own borders so long as nobody else is disturbed. The days when genocide in Rwanda and Kosovo can be ignored are over.

That's Mr Blair's vision at least. It remains to be seen whether the neocons share that perspective, or merely have a narrower vision of US self-interest that is restricted to the "axis of evil".

Which brings us to the second strand of Mr Blair's thinking. He really does believe it is right to oust Saddam. Prior to September 11th it would have been impossible to act on that belief. That is another key way in which things have changed. This time, the neocons and Mr Blair agree on both the means and the end.

That would never have happened before. A half-baked social democrat like Mr Blair, who probably used to march with CND in his youth, would never have gone down this road.

Observe the profound changes that September 11th have wrought in this man. He believes that the threat from unstable regimes and international terrorism is real and is big enough that the Western way of life is under serious and immediate threat.

He obviously believes that the world has never faced anything like this before, including the Cold War years. He gets it, old Europe does not.

What's next? A new benign world order - including moves to kick start the Israeli/Palestinian peace process - or another major problem with A.N. Other tin-pot dictatorship/failed regime/ sponsor of global terrorism? The list of potential candidates is, of course, a long one.

Mr Blair's hope must be that the Iraqi campaign sends a sufficiently credible threat to such countries so that they get the "don't mess with us" message.

But crunch time comes if and when even he cannot agree to whatever is dreamed up by the Washington warriors.

There are so many unknowns in all of this, so much speculation, so many different ways that things could evolve. We might, hopefully, be ushering in a new golden age but it would seem foolish to bet on it just yet.

Which is why I was so puzzled last week to see financial markets rushing to forecast that all is now well with the world. I sincerely hope they are right. Second thoughts at the beginning of this week were, perhaps, inevitable. Markets, like many other things, will continue to be reactive as events unfold.

• Chris Johns is chief strategist at ABN-Amro Securities, London. All opinions expressed are entirely personal.