Parliament had the luxury yesterday of debating at length the quality of the evidence of Syria’s use of chemical weapons and the legality of responding with force. It was better to have the debate than to scrap it, because no military intervention should be undertaken lightly.

The result of the vote, however, was a disaster. It was a disaster for the prime minister who misjudged his party. It was a disaster for the country, which turned its back on its tradition of standing up to tyranny. It was a disaster for the western alliance, split apart by British failure to stand with its allies. And most important of all, it was a disaster for the people of Syria, who know that they have fewer friends in their hour of need.

The only crumb of comfort is that the vote will not have stopped western action altogether. The truth that few speakers were ready to acknowledge is that no vote in the Commons will determine when, or if, the regime of President [Bashar] Assad falls and the suffering of the Syrian people stops. The only western government with a potentially decisive role in this crisis is that of the United States.

When the uprising against Assad began it was possible to argue that the US had no compelling strategic interest in its outcome. That situation ended when Mr Obama described the use of chemical weapons as a red line that would change American calculations. That line has been crossed and crossed again.