This morning the UK wakes up with the spectre of one man hanging over Westminster, the UK and the Anglo-American relationship.

The last time a British prime minister was defeated by the Commons on a war motion was 1782 when MPs refused to go on fighting – of all people – the restless Americans wishing for independence.

It’s taken Tony Blair, Iraq and the dodgy dossier to bring about such a historic moment again in our land.

The travesty, the falsehoods went deep over Iraq. Last night we found out just how deep into the political psyche of the nation. After Iraq, if a PM said there are trees in the rainforest you’d need to send for proof.

Tony Blair’s intervention in this campaign-to-bomb undoubtedly was the worst nightmare for Cameron and Obama. Down there with any putative Dubya endorsement. A political misjudgement. A PR catastrophe.

30 blair r w Spectre of Blair haunts Syria war

William Hague’s protestations that this was nothing to do with Iraq when everyone – surely himself included – knew it was everything to do with Iraq looked what they were, desperate Canute-like flailing against the long-flowing tide of public suspicion.

So come the put-up-or-shut-up moment of truth in the Commons and – post Iraq – Mr Cameron’s two sides of A4 were never going to cut it with MPs whose radar was switched to public mood.

Other blogs from Channel 4 News

After last night’s Syria vote, has Britain become the new Sweden? – by Gary Gibbon

Syrian refugees admiring and baffled after UK’s ‘no war’ vote – by Lindsey Hilsum

Cameron’s ‘judgement’ call

The PM said the evidence could never be 100 per cent and that it required a judgement call.  But post Iraq, no government can rely on YouTube and shadowy intelligence as a pretext for bombing another country as David Cameron did (as Kerry and Biden have done in the US).

Equally, what politician – post-Iraq – would reasonably even attempt the ploy of saying to the British public that we have evidence but we cannot show you? Trust daddy, he knows best.

Once upon a time – ante Blair, ante Iraq – it might have worked. Now it looks either desperate or plain daft.

Worse, even had he produced intelligence-based evidence, many would still not believe it. When the credibility of MI6 and 5 have been damaged to that extent, you begin to see the Iraq legacy for the catastrophe that it is in terms of voter confidence in the key public institutions of state.

So yes, William Hague, it has very much indeed been about Iraq.

Post Iraq – in the White House and Pentagon – the supine obedience of the British parliament is no longer quite the given that it was.

So, irony of ironies, it may well prove that that most abject and dutiful slave to US foreign policy, Anthony Blair, is the man who finally made it possible for the British parliament to think and decide upon matters of warfare all by itself and, on occasion, to say no – not just to the prime minister, but to the White House.

The march against the Blair-Bush Iraq invasion was the biggest these islands had seen, at least since the Chartist rallies. And it probably outnumbered even them. It was the mother of all focus groups showing its disgust over the coming mother of all battles.

It was utterly ignored.

Last night, the mother took her revenge with dramatic eloquence.

Follow @alextomo on Twitter