How can Mr Blair persuade the voters to go to war for a man they think is a fool?

The problem is that the liberals have written the script. The British public are convinced that George Bush is just a dim cowboy

Our Prime Minister is an enigma, perhaps even to himself. But what else would one expect of a consummate opportunist who has a profound belief in his own moral credentials? This search for morality has led him in unpredictable directions; hence the contradictory nature of last week's performances.

On Monday, in white tie at the Lord Mayor's Banquet, the PM was in command. On terrorism and the international picture, he spoke in sombre terms, but seemed at ease. On Wednesday in the House of Commons, he turned to the domestic agenda, and what a contrast. His delivery was scratchy, uncertain, graceless and petulant.

Here, I must apologise to my readers. Last week I predicted that the Queen's Speech would be stale stew. I was wrong. It was not nearly so nourishing. Indeed, it was one of the worst Queen's Speeches for many years. Decomposed well beyond staleness, it was so covered in green mould as to be of value only to Sir Alexander Fleming's successors.

Five and a half years ago, no one would have predicted that Mr Blair would evolve into a premier who would be so at home in foreign affairs and so frustrated with his domestic agenda. But there is an explanation. He underestimated one set of tasks and another set of resources.

Back in 1997, Tony Blair believed that he had brought off a coup. He had persuaded the British people that the Tories had virtually abolished public expenditure, when they were actually spending £300bn a year. So all he needed to do, thought Mr Blair, was to bring in spin doctors, apply a few licks of paint, ensure that the money was spent effectively – and everything would be fine. He has gradually realised how difficult it is to turn public spending into value for money.

Except when it comes to the armed forces. At the beginning of his premiership, Mr Blair had given little thought to military matters. Like any sensible person encountering the military for the first time, he was immediately struck by their efficiency. Ask a domestic official to deal with a problem, and six months later, when asked for a progress report, he will announce that the committee which he had set up had concluded that there were not enough resources. Ask a general to tackle a problem, and he will ask whether he can have until close of play on Friday.

Mr Blair is also much more impressed than he expected to be by the upper echelons of the Foreign Office and by the security services. Here, he is fortunate in the key appointments. The five most important figures – David Manning, his foreign affairs adviser; Michael Jay, the head of the Foreign Office; Richard Dearlove of MI6; John Scarlett, who runs the Joint Intelligence Committee; and Jonathan Powell, on the political side – are not only men of the highest ability, they work well as a team.

This was, of course, assisted by Robin Cook's removal from the Foreign Office; Mr Cook's presence can instantly render any team dysfunctional. Jack Straw is a team player who wryly accepts the fact that Mr Blair is really his own Foreign Secretary, with David Manning as his deputy.

Nor is this only a domestic team. It is also a transatlantic one. Past premiers have had good relations with presidents, but the London-Washington axis is now something special. Not even in the days when Ronald Reagan was half in love with Margaret Thatcher was there such a depth of trust, affection and respect between the respective foreign, defence and security chiefs. Our PM has a much more harmonious relationship with the President than with his own Chancellor.

But as Mr Blair might have reminded his Guildhall audience, such harmony does not guarantee success. The defeat of Islamic terrorism is as elusive as ever. Western intelligence services have not been able to penetrate al-Qa'ida's networks, which is hardly surprising. There are not many agents who could pass themselves off as Muslim fanatics. Electronic monitoring has brought limited success, but whether or not Bin Laden is still alive, al-Qa'ida is far from destroyed. It may have lost its Afghan bases, but it can still operate from the badlands of Pakistan as well as in Yemen and Somalia, where central government has little control over large areas of the hinterland.

There is no easy solution. America is not about to cease to be America, or to support Israel, any more than al-Qa'ida will renounce its hatred of everything America stands for and its intense desire to destroy Israel. Nor will it cease to be able to recruit militants from the alienated young of the Muslim world.

A few months ago, the Americans, more optimistic then than now, decided to place their faith in a revolution in the Arab world. Following the overthrow of Saddam, they were looking to the emergence of new structures which could offer hope of material and political improvement. At best, however, this would be a long process, and stage one, the fall of Saddam, is still in a limbo of postponement.

This condemns the Americans to a double odium, of seeming simultaneously overbearing and weak. It must be remembered that the drift to 11 September was not caused by American strength, but by American weakness. Al-Qa'ida was able to hit US targets without incurring effective retaliation. Since the overthrow of the Taliban, there has been a further stuttering in retaliatory momentum. The US would do well to remember the Latin maximoderint dum metuant; let them hate, so long as they fear. Fearless hatred is a lethal opponent.

It is unlikely that Mr Blair will take much comfort from the classics. Since 11 September, he has acted more boldly than usual, as if he were determined to vindicate his claim to be a moralist, and banish the charge of opportunism. A man who does not make a choice of breakfast cereal without taking advice from a focus group was prepared to be at odds with public opinion, and to embark on a course which increased the risk to the UK.

As the IRA often discovered, the British population is stoical under fire. But would that necessarily apply in the cause of Islamic terrorism?

The problem for Mr Blair is that the liberals have written the script. About three-quarters of the British public are convinced that George Bush is a cowboy dunce surrounded by warmongers. Though this is a childish caricature, it will not be easy to persuade the British to support a President whom they chronically underrate.

We are now in danger. The secret services and the Special Branch are doing everything possible to monitor potential terrorists, and there have been successes, as in the past few days. But if we are to defeat terrorism, we will need to rely on one of Mr Blair's most durable attributes. We will have to be lucky.

When it comes to international affairs, as opposed to domestic ones, Mr Blair deserves his good fortune. In dealing with terrorists, however, good fortune cannot indefinitely be guaranteed.