It is a measure of the extent to which British involvement in Iraq is a no-win situation that the scaling down of troop numbers announced yesterday can be seen as too little, too late yet too much, too soon. A procession of senior military figures has warned that British forces are dangerously overstretched. The proposed cut in troops around Basra from 7100 to 5500 effectively will free capacity that can be redeployed against the Taliban in Afghanistan. Soon Britain will have more troops there than in Iraq but, given the imminence of the spring offensive in Helmand, many believe the switch is overdue.

After decades under a brutal dictatorship and because of the ill-advised disbanding of the Iraqi army, Iraqi soldiers have proved unable or unwilling to take on leadership roles. The longer British troops are active on the streets of Basra, the more distant the moment of truth when the newly-formed Iraqi brigades are forced to take the initiative. Unlike Baghdad, where much of the violence is between Sunni and Shia, in overwhelmingly-Shia Basra the insurgency against allied forces is the focus of the bloodshed. Ergo, the British presence is counter-productive.

Mr Blair wants "the next chapter in Basra's history to be written by the Iraqis". But if Iraqi troops prove incapable of controlling the incipient mayhem in the city - its criminal population swelled by refugees from the American offensive in Baghdad - that chapter could be a horror story. And, worse than that, British troops cooped up in the airbase outside the city could be sitting ducks. In a worst-case scenario, fresh British reinforcements may be required to fill the breach. Already there are doubts that the remaining troops will be capable of protecting the American supply route from Kuwait and patrolling the long porous border with Iran, as well as backing up Iraqi troops.

If the Prime Minister had heeded the warnings of those, including The Herald, who opposed the British invasion, we would not be in this position. But we are and, consequently, we have a residual responsibility to the Iraqi people. British troops have acted with the utmost bravery and professionalism throughout this conflict. It is no disrespect to them to say that it is outrageous of the Prime Minister to suggest, as he did in his narrative of events yesterday, that this is a withdrawal in the wake of success. With reconstruction virtually stalled, corruption endemic and the confidently predicted "beacon of democracy" in a state of paralysis, this is a disengagement in the face of an impossible situation.