I think I would like to use an analogy to describe the situation.
Think of the situation where a doctor tells the patient that one of his arteries is getting blocked. The doctor says there is definite blockage, its a 'slam dunk.' So they proceed with the operation to free his arteries from the danger of the blockage. Half way in the operation the doctor realised, opps there is no blockage, the operation was not necessary. What then is the doctor to do? You do not expect the doctor to stop the operation and leave the person still cut open and walk away do you? You need to close the gaping hole in the person's body.
Here is an interesting letter sent by more than 50 former British ambassadors to Tony Blair:http://news.bbc.co.uk/2/hi/uk_news/politics/3660837.stm
Here is the extracted the part of the letter dealing with Iraq.
We the undersigned former British ambassadors, high commissioners, governors and senior international officials, including some who have long experience of the Middle East and others whose experience is elsewhere, have watched with deepening concern the policies which you have followed on the Arab-Israel problem and Iraq, in close co-operation with the United States.
The conduct of the war in Iraq has made it clear that there was no effective plan for the post-Saddam settlement.
All those with experience of the area predicted that the occupation of Iraq by the Coalition forces would meet serious and stubborn resistance, as has proved to be the case.
To describe the resistance as led by terrorists, fanatics and foreigners is neither convincing nor helpful.
Policy must take account of the nature and history of Iraq, the most complex country in the region.
... The military actions of the Coalition forces must be guided by political objectives and by the requirements of the Iraq theatre itself, not by criteria remote from them.
It is not good enough to say that the use of force is a matter for local commanders.
Heavy weapons unsuited to the task in hand, inflammatory language, the current confrontations in Najaf and Falluja, all these have built up rather than isolated the opposition.
... We share your view that the British government has an interest in working as closely as possible with the United States on both these related issues, and in exerting real influence as a loyal ally.
We believe that the need for such influence is now a matter of the highest urgency.
If that is unacceptable or unwelcome there is no case for supporting policies which are doomed to failure.