David Cameron has lost far more than the argument over Syria. He put his credibility on the line tonight, and lost. This is not just an extraordinary defeat but a spectacular political misjudgment, as I say in my Daily Telegraph column tomorrow. There will be a great many more questions asked tomorrow: from a sleepy summer recess, Cameron has conjured up one of the most spectacular parliamentary defeats in modern political history. The first such foreign policy defeat since 1782. What on earth was No10 thinking? That it could depend on Ed Miliband’s support? (He spoke abysmally today, by the way, offering a “sequenced roadmap”, and his amendment was defeated. There are only losers in today’s vote.)

A third of the Tory party is opposed to a Syria strike, the public is against it by a ratio of two-to-one. And yet still, the Prime Minister of a hung parliament tries to ram through a vote for military action using the same methods and logic as Iraq. Their own dodgy-looking dossier. The own Attorney General legal advice (or sections of it), claiming that it’s all okay really. And a Defence Secretary who went on Newsnight and actually spoke about taking action against “Saddam” rather than Bashar Assad. The whole thing looked like an Iraqi Groundhog Day.

I am personally sympathetic to Cameron’s arguments about Britain’s role in the world.But to force a vote in this way, with such shoddy preparation and so little forethought, will outrage Cameron’s allies. Why gamble all this political capital in such a way? Make no mistake: this is a foreign policy vote, but the result weakens the government’s overall authority. Needlessly. All that political progress made over summer: wiped out. Already, Ed Miliband is trying to rewrite today’s history in a way that involves Plucky Ed standing up to America. The same Ed who sounded all up for a Syrian strike in interviews on Tuesday morning.

As the leading article in this week’s Spectator says, an attack in Syria would be a war without a purpose. The more questions asked about this, the more questions arise. And it was the absence of answers to very good questions which, I think, sunk Cameron today. His case for intervention was not very well thought-through. Holes were picked in it all day, by everyone from Jack Straw to the Archbishop of Canterbury.

But there are always doubts when countries go to war. The biggest question is one of trust. Cameron was asking for that trust today, and he didn’t get it. He took a massive gamble, and suffered a massive defeat. It was one from which he will, I suspect, take some time to recover.