Operation Blair Legacy is in full swing. He may not have been greeted by cheering crowds, as predicted in that leaked memo last year, but the Prime Minister is devoting his last weeks in office to shoring up his reputation. He is pinning his hopes on elections in Northern Ireland leading to a resumption of devolution. He will make more speeches to claim that it is he who is setting the pace on tackling climate change. But, as he and his aides admit, one issue will define his time in office: his decision to go to war in Iraq.

It is in this context that his announcement of a phased withdrawal should be seen. The cuts anticipated - 1,500 within a few months, out of the 7,100 troops serving - will take place slightly more slowly than originally envisaged. The significance lies in the fact that they are happening at all, just as the Americans' "surge" begins across the rest of Iraq.

Britain's claims about its role in Iraq have long produced reactions ranging from mirth to indignation in Washington. Even before President Bush's last throw of the dice, sending in 21,500 more troops, the UK involvement was significantly smaller than the American one, and less complex. The Sunni-Shia conflict, which we reported on in our 12 February issue, is not so acute in the Shia-dominated south of Iraq.

When Blair summoned the courage on 21 February to address MPs on Iraq, he was unconvincing in his justifications and, as ever, selective in his use of history. And yet, he may have been technically correct when declaring the four-month Operation Sinbad over. The four provinces notionally under UK control are being handed back. British troops have performed professionally, even though several cases of maltreatment of the population have been proven. The soldiers have done their best to work with governors and train indigenous security forces.

It is not the British army's fault that for many months the troops have been able to get about only by helicopter, and that every time they have left their bases they have risked their lives. It is not their fault that they are leaving behind an abject mess. It is not their fault that they were given this task in the first place. It is worth remembering the warning last October by the head of the army, General Sir Richard Dannatt, that the presence of British troops in Iraq was exacerbating security problems.

It is worth remembering too, as the 101st British serviceman is buried, that Blair's main contribution to the US war effort was far more political than military. It was he, virtually alone, who gave Bush the veneer of respectability to flout the United Nations. British forces, as Donald Rumsfeld awkwardly reminded ministers on the eve of war, were not vital for the invasion. There were, he famously said, "workarounds" if the British had a change of heart.

Only a month ago, Blair declared that any attempt to set an arbitrary timetable "would send the most disastrous signal to the people we are fighting in Iraq". His legacy, it seems, comes first. Opportunism knocks.

The withdrawal is now expected to be completed during 2008. It would be unwise of Gordon Brown to allow the politics to get in the way of military considerations, but for as long as British soldiers remain in Iraq, he will not be able to move on from the conflict. He should not wait for the final withdrawal before launching a full inquiry. As polls show, the public is growing disenchanted with this government and sceptical about Brown's ability to produce a change. As an incoming prime minister, Brown has the opportunity to rejuvenate Labour's fortunes and revive morale. He will need a raft of announcements and initiatives on the domestic front to do so.

Nowhere is the need for a clean break greater than in the international arena. Never again should Britain shun the vast majority of its allies or multilateral institutions when considering military action. Never again should ministers privately express reservations about war, only to vote it through. Ultimately, however, the responsibility lies with one man. As he brings down the curtain on Britain's war in Iraq, Blair is hoping that memories are short and the verdict will be benign. A shoddy war has produced a shoddy political exit.

Conversions and conversions

If you think that the proliferation of number games such as sudoku speaks of a nation at ease with adding up, think again. A survey by an adult learning association has found that nearly half of us (49 per cent, if you know what we mean) feel that poor numeracy is holding us back. One in five of us can't deal with different currencies or work out the best-buy baked beans when the tins are different sizes, and one in three of us can't convert fractions to decimals (that's 1/3 or 0.33).

And here's a worrying thing. While we are counting our change on our fingers and squinting at the euros as we buy café con leche in Málaga, the money we lose is adding up to £823m a year. That is more than a tenner each.

So, surely Ivan Massow, once the poster boy of the "No Euro" campaign but now revealing himself in the NS as a surprise convert to the single currency, has got it right. Wherever you stand on federalism or the constitution, the euro is an issue apart. It has become the world's currency. You can take it anywhere, and its adoption by the UK would free businesses from the vagaries of exchange commissions and fluctuations. Moreover, we stand to gain an astonishing £5.4bn lost in exchange commission.

The naysayers, who dominate both main political parties, will rehearse their points about monetary straitjackets and other Continental horrors. Each point can be calmly rebutted. Most of these politicians have declared the debate over. We shall see.