Donald Macintyre: Shoulder to shoulder with Mr Bush - but how long will this unity last?

'Instinctively, many MPs don't want the British government to give America a blank cheque'

t was on the occasion of a declaration of war with Spain in 1739 that Tony Blair's first predecessor, Robert Walpole, observed: "They now ring the bells, but they will soon wring their hands." Mindful perhaps of just that sentiment, the House of Commons, especially but not only its huge Labour majority, indulged in very little bell ringing during its emergency debate yesterday. There were, as there always are, one or two silly and inappropriate speeches. There were several good ones, including a passionate plea against the demonisation of British Muslims by the new MP for Birmingham, Perry Barr Khalid Mahmood. But perhaps the three minutes in a deadly silent chamber were the most eloquent of all.

But in setting the tone, Mr Blair also studiously eschewed just the kind of "bell ringing" rhetoric that Walpole lamented and that President Bush seems incapable of avoiding with his now increasingly frequent references to war. Mr Blair undoubtedly impressed much of his own side with his – and Jack Straw's – warning that terrorists would use chemical, biological and even nuclear weapons if they could. But he probably impressed many worried Labour MPs just as much with his clear call for the reinvigoration of the Middle East peace process. This matters. Because, as ever, there are still quite a lot of Labour MPs who worry when they see their own leaders giving what they fear may be unequivocal backing to a Democratic Americanadministration, let alone a Republican one.

Indeed, when the House of Commons unites, it's always worth taking a reality check. This isn't to say that the unity isn't real – only that it may not last for ever. In his first speech as Tory leader Iain Duncan Smith was responsibly bi-partisan, stressing his desire to back the Government rather than to imply that his was the only true voice of Atlanticism as some of his more zealous supporters believe. And on the Labour side even potential dissidents like George Galloway and the respected Tam Dalyell were relatively restrained. It isn't, for example, every day that you hear Mr Galloway saying he agrees with Peter Mandelson, in this case for saying that the greatest test of Western action against terrorism is that it should be effective. (Mr Mandelson's speech, also thoughtful, urged the US: "Don't get mad, get even.")

But the fact remains that there are different instinctive responses within the British legislature. There are an (increasingly small) number of MPs on the left who retain unshakeable suspicion of the US. Equally, however, there aren't that many Labour and Liberal Democrat MPs who don't have a suspicion of and instinctive distaste for the thirst for war, almost at whatever cost, which they fear could yet develop within the US and nourish rather than prevent further terrorism. Instinctively, most don't want the British government to give the White House – a phrase which cropped up repeatedly yesterday – a "blank cheque" for retribution.

Many Tories made that same point yesterday, in the Lords as well as in the Commons. But the Tory leadership victory of Iain Duncan Smith does reinforce a very strong streak of not only pro-US but also pro-Bush opinion in the dominant section of it.His new Defence spokesman, Bernard Jenkin, explicitly took issue with the "blank cheque" terminology insisting that the US administration would not do anything which should not command unequivocal support. It isn't easy to imagine circumstances in which the Tory leadership would part company with the US in the coming months. It is quite easy to imagine circumstances in which quite large numbers of Labour MPs might, if the response from Washington is judged disproportionate and counter-productive.

Which is why this is a test for Tony Blair as it is – in much larger way, of course – for President Bush. In the nightmare scenario, the US embarks on a bombing raid of Afghanistan – which both kills many innocent civilians and leaves Bin Laden's training camps intact. The Tories step up their pro-American rhetoric just as Labour support starts to ebb away. And Mr Blair is left on a difficult road.

That isn't how it looks at present. True, the debate within Labour about missile defence – on which Mr Blair has been supportive – will remain intense. Most ministers with an interest in the issue believe that one certain consequence of Tuesday is that the administration will now definitely go ahead with MD. Some MPs may rethink their opposition to British help for the project too. Others, though, will argue strongly that the catastrophe shows that the money could be better spent on other forms of security – like "doubling the Marine Corps and putting soldiers on every plane," as one minister put it yesterday.

But that's some way off. And in the meantime Mr Blair appears to have gone a long way to reassure his own MPs in his speech yesterday. Most appear to appreciate the sureness of his handling so far – which they freely contrast with that of the US President. The majority appear, too, to buy into the argument that Mr Blair's internationalisation of the conflict affords the best chance of exerting – albeit limited – influence. Equally, they were impressed by Mr Blair when he pointed out the administration had proceeded with great care so far. More sophisticatedly, they note that the anti-isolationist Secretary of State, Colin Powell, appears to be strengthening in authority in Washington.

So while, in some circumstances it may not last for ever, the unity is indeed real enough for the present. That isn't to deny that the majority view in the Commons was strongly in favour of a measured, productive response, and strongly against eye-for-eye retribution. In the Lords, Lord Howe, the former Tory Foreign Secretary, spoke for the prevailing mood in both houses when he quoted a general who had himself quoted a historian saying that "Of all the responsibilities of power, restraint is the one that impresses most". The historian was Thuycidides. The general was Colin Powell.

d.macintyre@independent.co.uk