Mr Blair will try to rally the nation, but his lies mean that even his party may not listen

As a result of the PM's mendacity, there has been a double revulsion, against his war, and against him

This is when it would help to have a Prime Minister who was trusted. On all the big questions about Iraq, Tony Blair is right. We may agonise over Kenneth Bigley's fate, but no sane British government could ever make concessions to save the life of a hostage. That might rescue one victim. In so doing, it would create 55 million potential victims.

Mr Blair is also right to insist that we must keep right on to the end of the road and complete our mission in Iraq. If they were not consumed by anti-Americanism, even those who oppose the war ought to see the folly of abandoning Iraq now. Were we to do so, Baghdad might fall under the control of a worse regime than Saddam's, and inasmuch as it is not yet a crucible for international terrorism, it would rapidly become so.

The West would be despised throughout the Muslim world, with our allies rushing to save themselves by disowning us. There would be a greatly increased risk of a nuclear war between Israel and Islamic nations during the next decade.

Duty and self-interest point in the same direction. In the run-up to the war, Colin Powell told Mr Bush about a notice in an antique shop: "If you break it, you own it". We broke Saddam's regime. We now have to mend Iraq.

The PM was also correct when he warned the press about the danger of mass hysteria in their coverage. Mr Bigley is an admirable fellow who deserves better, as does his family and especially his aged mother. But he is only one man. In the great sweep of events, his fate counts for little. Yet some papers have given the impression that the entire country is now in trauma. That is not only bad journalism; it is dangerous talk.

Among Islamic fanatics, it is an article of faith that Westerners are feeble, decadent and cowardly. Whatever our technological prowess, we are so obsessed by pleasure-seeking as to be incapable of enduring hardship or displaying courage. Kill enough of us, and we will run away.

Over the past few days, the British press has hardly set out to refute that view. Terrorists tend to strike when they think they see weakness. No group planning to bomb the UK will have been discouraged by the recent reaction of the media.

In such circumstances, any premier would be entitled to do as Mr Blair has, and warn of the dangers that terrorists will manipulate the media - and that is the problem. This PM cannot do so with any conviction. Satan cannot rebuke sin. Tony Blair on media manipulation; the next thing we know, he will be assuring us that he is a pretty straight sort of guy. Mr Blair does not seem to be aware of the extent to which he has forfeited public confidence - and it is all his own fault.

There is an Arab proverb which now summarises many voters' opinion of their PM; "Fool me once, shame on you. Fool me twice, shame on me". These days, when they listen to Mr Blair, many people are primarily concerned to avoid being fooled again. It does not matter that Lord Hutton exonerated the PM or that the formidable criticisms in the subtle small print of the Butler report have been largely ignored. The public got the message that the PM had lied on crucial matters: intelligence, national security, peace or war. That is the worst breach of faith which a prime minister can commit. For it means that when he needs to be listened to he will not be; that when he has to rally the nation, the nation will not respond.

He is still trying to repair the damage by tricks and shams. Over the weekend, he tried to evoke the Second World War. Blair as Churchill; those clothes are far too big for him. When Churchill became war leader, he promised blood, sweat, toil and tears - not headlines, sound-bites, spin and lies.

There is a terrible irony. Mr Blair embraced the American cause on Iraq for the noblest of reasons. He was persuaded by the neo-Conservative analysis as expressed by George Bush: that until much of the Middle East ceased to be a Mordor of failed states, terrorism would be endemic, and that all roads to improvement led through Baghdad. Iraq could have been Tony Blair at his best, but only if he had summoned the moral authority to throw behind the cause.

There, he did not even try, because he did not trust his country, his party or himself. He also thought it was safe to duck the challenge because, like almost everyone else, he was certain that Saddam had weapons of mass destruction and that he could safely rest his case on them.

George Bush was equally in error over WMD. From the outset, however, he was much more forthright about his broader goals. Moreover, the US Congress had already endorsed a policy of regime change in Iraq.

Mr Bush had one further advantage. Out of a blue sky, American was subjected to an unprovoked attack. Since then, it has been possible to convince enough American voters that the US cannot guarantee its safety merely by defending its own borders. That is why the President is ahead in the presidential polls.

In Britain, it is different. The Americans can be persuaded that it is necessary to act to prevent another 11 September. The British are more likely to believe that by acting in support of the Americans, we will provoke an 11 September on our own soil.

There is no doubt that by committing ourselves to be America's foremost ally we did indeed increase the short-term danger to ourselves. Again, that is a matter for political leadership. Had he tried, Tony Blair might have been able to carry the argument that such an enhanced risk was a price worth paying for long-term security.

But that would have required honesty, which was not forthcoming. As a result of Mr Blair's mendacity, there has been a growing and double revulsion, against his war, and against him personally, as is demonstrated by the latest polls.

Although this was true before Mr Bigley was kidnapped, he has been a catalyst. In electoral terms, he is the most important hostage since the captives from the American embassy in Iran. He could influence the outcome of the next election.

That is unlikely to console his family. If only there were some consolation - but he is in the hands of men who appear to enjoy cutting other men's throats. If only we were less powerless, but however much distress his mother suffers and however moving the appeals on his behalf, the Government must stick to its course.

This becomes steadily harder when more and more of the public believes it to be a dangerous and immoral course. It is not inconceivable that Tony Blair will manage a successful counter-attack during this week's Labour Party conference. In the past, when he has needed to make a good speech, he has never failed to do so. Yet he will now find it far more difficult. Both in the hall and in the country, a lot of those who hear his speech will be determined not to listen, and they can hardly be blamed for refusing to give a hearing to a proven liar.