I suspect we know less than half of what actually happened outside the city jail that day. But if the first duty of any officer is the protection of his own men, this must count as a brilliant operation. Enough British soldiers have died recently for us to offer thanks that four of them, on this occasion, were saved.

The diplomatic repercussions are something else. This was an action directed against the Iraqi police, the very people the British are meant to be training, and who represent the front line in the battle against terrorist attacks. It is they who will be responsible for security when coalition forces finally pull out, and they who have been the principal victims of the insurgents. Things have gone badly wrong if, as appears to have happened, special forces and Iraqi police were involved in a shoot-out, ending in the death of one policeman and the arrest of the two soldiers. There have been numerous reports recently that hostile militias have infiltrated the police, and even taken control in some areas, but if they are now involved in internecine warfare against coalition forces, then that is a grim development, introducing an element of instability that even Baghdad has not had to contend with.

None of this merits the panic reaction of those who have seized on these dramatic events as evidence that British troops should announce forthwith the date for a pullout, leaving Basra to the tender mercies of Moqtada al-Sadr’s al-Mahdi Army. This was a violent attack but, as Brigadier John Lorimer, who was in charge of the operation, pointed out, it involved a small crowd of fewer than 300 people. Colonel Tim Collins, who commanded the 1st Battalion of the Royal Irish Regiment during the invasion, observed on Newsnight that barely a dozen petrol bombs were thrown — “no worse than a night on the streets of Belfast”.

To back down in the face of a mob assault would be to send a signal that would be welcomed by every militia gang jockeying for power in Basra in the run-up to the referendum on Iraq’s constitution, and invite the open warfare that the south, for all its troubles, has hitherto avoided. Nothing would be more likely to fan the flames of insurrection. Above all, it would be the worst possible message to send to British soldiers patrolling the streets of Basra, who are attempting to guarantee the security of its citizens.

No one suggests that the situation in Iraq is other than grim, the daily statistics of death and destruction so shocking that we find it hard to absorb them, the life of its people a constant struggle for survival.

Looking back, it was clearly premature, if not complacent, to suggest that British forces were better at low-intensity operations in the south than the Americans were in the north. More should undoubtedly have been done to counteract the militias who are now subverting the police, to involve the warring factions in the political process, to challenge the al-Mahdi militants. And more should have been invested in improving the basics of daily life; much of the trouble now spilling on to the streets has come about because the remarkable patience of ordinary Iraqis is finally wearing off.

None of that justifies a failure of nerve at this, of all critical times. With a constitution to vote on, a government to take effect, and a civil war to prevent, now is the worst time to start talking about withdrawal. Recent evidence that Tehran is beginning to orchestrate some of the violence suggests that any vacuum left by a coalition withdrawal would be filled by extremism of the worst sort. Even Colonel Collins, who has come round to the view that an exit strategy must be devised, concedes that there are certain basic commitments that must be fulfilled before that can happen. “We have dragged the Iraqis into a deep hole,” he said, “and we must help them out of that hole before we even think about getting out ourselves.” The political process must be given a chance. The economy must be given a chance. Basic services must be guaranteed.

The Iraqi security forces, for which, remarkably, recruitment continues despite horrendous attacks, need training, support and the opportunity to demonstrate that they can apply law and order impartially across the religious divide. The borders of the country must be secured.

This is not an argument about the rights and wrongs of the invasion of Iraq, about neoconservatism, al-Qaeda or the politics of oil. It is about the fate of a people who were promised a bright future and who have seen their country reduced to a battlefield. It is about the responsibility of those who took it upon themselves to offer democracy and have delivered barely a shadow of it. It is about the hope that thousands of Iraqis expressed when they exercised their right to vote.

It is, finally, about the principles that our soldiers still believe they are defending and for which, as we have been so graphically reminded, they are prepared to risk their lives. They are principles that we should take as seriously as they do.

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