Jeremy Corbyn had been forced to back down once before the start of today's shadow cabinet meeting on Syria, offering Labour MPs a free vote on air strikes against Isis. By the end of the two-hour gathering, he had backed down twice.

At the start of the meeting, Corbyn's office briefed the Guardian that while a free vote would be held, party policy would be changed to oppose military action - an attempt to claim partial victory. But shadow cabinet members, led by Andy Burnham, argued that this was "unacceptable" and an attempt to divide MPs from members. Burnham, who is not persuaded by the case for air strikes, warned that colleagues who voted against the party's proposed position would be "thrown to the wolves" and said that he would not be a part of a "sham shadow cabinet". The vote would be free in name only.

Jon Ashworth, the shadow minister without portfolio and NEC member, proposed a logical solution: Labour's policy should remain the motion passed by this year's conference, which is open to competing interpretations (most believe the tests set for military action have been met). Party policy could not be changed without going through a similarly formal process, he argued. In advance of the meeting, Labour released a poll of members (based on an "initial sample" of 1,900) showing that 75 per cent opposed intervention, regarded by some as an attempt to bounce the party into opposing air strikes,

When Corbyn's team suggested that the issue be resolved after the meeting, those present made it clear that they "would not leave the room" until the Labour leader had backed down. By the end, only Corbyn ally Diane Abbott argued that party policy should be changed to oppose military action. John McDonnell, who has long argued for a free vote, took a more "conciliatory" approach, I'm told. It was when Hilary Benn said that he would be prepared to speak from the backbenches in the Syria debate, in order to avoid opposing party policy, that Corbyn realised he would have to give way. The Labour leader and the shadow foreign secretary will now advocate opposing positions from the frontbench when MPs meet, with Corbyn opening and Benn closing.

The meeting had begun with members, including some who reject military action, complaining about the "discorteous" and "deplorable" manner in which the issue had been handled. As I reported last week, there was outrage when Corbyn wrote to MPs opposing air strikes without first informing the shadow cabinet (I'm told that my account of that meeting was also raised). There was anger today when, at 2:07pm, seven minutes after the meeting began, some members received an update on their phones from the Guardian revealing that a free vote would be held but that party policy would be changed to oppose military action."It's already on Twitter," said one shadow cabinet minister. Corbyn responded by telling members to stop tweeting from the room only to be informed, to his surprise, that the briefing originated from his office. This "farcical moment", in the words of one present, only hardened shadow cabinet members' resolve to force their leader to back down - and he did.

With Labour MPs guaranteed a free vote on air strikes, David Cameron is all but certain to achieve the "clear majority" for military action that he wants.

In a statement released following the meeting, a Corbyn spokesperson confirmed that a free vote would be held but made no reference to party policy:

"Today's Shadow Cabinet agreed to back Jeremy Corbyn's recommendation of a free vote on the Government's proposal to authorise UK bombing in Syria.

"The Shadow Cabinet decided to support the call for David Cameron to step back from the rush to war and hold a full two day debate in the House of Commons on such a crucial national decision.

"Shadow Cabinet members agreed to call David Cameron to account on the unanswered questions raised by his case for bombing: including how it would accelerate a negotiated settlement of the Syrian civil war; what ground troops would take territory evacuated by ISIS; military co-ordination and strategy; the refugee crisis and the imperative to cut-off of supplies to ISIS."