By Nick Assinder
BBC News Online political correspondent
The fact that the Iraq Survey Group has found no weapons of mass destruction in Iraq is unlikely to provoke gasps of surprise in Britain.
Saddam: Wanted to produce WMD
This is, after all, the moment the prime minister has carefully been preparing voters for over the past few months.
His original line had been to urge his critics to let the ISG complete its work before jumping to conclusions.
By last July, however, he had changed tack and told the MPs on the Commons liaison committee that he had to accept the ISG had not found WMD "and may never find them".
By the time of his party conference speech last week, he had gone so far as to accept that the original intelligence on Saddam's supposed WMD had been wrong.
Most importantly, however, he also completed the process of appearing to shift his justification for the war away from WMD to the removal of Saddam Hussein.
"I can apologise for the information that turned out to be wrong, but I can't, sincerely at least, apologise for removing Saddam.
"The world is a better place with Saddam in prison not in power," he told the conference.
What Mr Blair cannot do, however, is suggest regime change was his real motive for the war - that may well have been illegal and, in any case, was not cited at the time.
So he has chosen instead to remind people the precise justification was to uphold UN resolutions which Saddam had defied for 12 years.
He will also now take much comfort from the suggestion by the inspectors that Saddam was certainly attempting to produce a WMD programme and was potentially even more of a threat than had originally been suggested before the war.
None of this, however, will alter the stark fact that claims used by the prime minister to back the war at the time - including the infamous 45 minute from attack suggestion - were wrong.
But that is now almost universally accepted, and any damage to the prime minister as a result has probably already been caused.
Indeed it is even possible that the ISG report's findings on the level of the potential threat posed by Saddam - because it is relatively new - will offer Mr Blair some ammunition to hurl back at his critics.
Critics are unlikely to accept that though. Former foreign secretary Robin Cook, who quit the cabinet over the decision to go to war, said the international community had always known Saddam Hussein had ambitions to have such weapons.
This was why there had been a policy of containment, says Mr Cook.
Indeed, he says, the report's findings that Saddam wanted WMD, but had none, suggested containment was a remarkably successful policy and the war was unnecessary.
The most troublesome aspect of the report for Tony Blair could be from its impact in the US.
President Bush or his officials have now accepted that Saddam was not responsible for 11 September (as many Americans had once believed), that there was no link between Baghdad and al-Qaeda before the war and, now, that there were no stockpiles of WMD.
These revelations are bound to be a factor the Presidential election campaign and if Democrat John Kerry defies the odds and wins as a result, that could spell trouble for Tony Blair.
Government advisers who attended the Democrat convention returned in no doubt about the level of anger felt by Kerry - and even President Clinton - at Tony Blair's stance on the war and continuing closeness to George Bush.
President Kerry would, of course, have to put much of that anger to one side in the interests of good diplomatic relations with Britain.
But many believe there would still be a significant cooling in trans-Atlantic relations.