With Labour, Lib Dem rebels and up to 70 Tory backbenchers all opposed to immediate British military action against Syria, David Cameron faced the prospect of parliamentary defeat. It was this that forced him to back down  last night and accept Ed Miliband's demand that no decision be made until after the UN weapons inspectors have presented their findings on last week's Ghouta massacre to the Security Council.
The government motion was published  and guaranteed that a "further vote of the House of Commons" would be held before any "direct British involvement". In line with Labour's position it stated that "[This House] agrees that the United Nations Secretary General should ensure a briefing to the United Nations Security Council immediately upon the completion of the team’s initial mission; Believes that the United Nations Security Council must have the opportunity immediately to consider that briefing and that every effort should be made to secure a Security Council Resolution backing military action before any such action is taken."
But if Cameron believed that a political consensus had been achieved, it looked like he was wrong to do so. Labour has signalled that it still plans to vote for its own amendment  this evening and has refused to rule out opposing the government's motion. A party spokesman said this morning that the party's amendment "provides a roadmap towards what must happen before any action is taken" and sets out "clearer criteria" than the government's.
The question now is what concessions Cameron would have to offer to secure Miliband's support and whether he is prepared to do so. Labour's amendment, for instance, suggests that military action should only take place if there is "compelling evidence" that the regime was responsible for the use of chemical weapons but the government's motion makes no such stipulation and notes that "the team’s mandate is to confirm whether chemical weapons were used and not to apportion blame". As things stand, it is hard to see how that divide will be bridged. But unless Cameron is able to win Labour round, or to persuade a sufficient number of coalition MPs to support the government, he faces the prospect of something unprecedented in recent history: parliamentary defeat on a matter of peace and war.