Brexit was expected by many to be the greatest flashpoint of the Labour conference. In defiance of the leadership, constituency parties submitted motions backing EU single market membership and free movement.

But in the members' ballot, not one of the eight motions chosen for debate was Brexit-related. The result owed much to Momentum, the pro-Corbyn grassroots group. It advised delegates not to vote for Brexit motions on the grounds that the issue would be officially debated on Monday (albeit in a far more anodyne manner). But more importantly, the debate would have pitted Jeremy Corbyn against a significant number of Labour members.

A Momentum source confessed to me that he had not expected the motions to be rejected and that he had underestimated the group's influence. Though a recent poll found that 66 per cent of Labour members back single market membership, delegates opted not to challenge Corbyn. A Momentum figure suggested that the decision to avoid divisive issues was a mark of the left's maturity and its desire to win (New Labour would similarly sideline controversial debates). "We shouldn't give ourselves the problems of government when we don't have the advantages of it," a party insider told me.

Momentum advised members to vote for motions on housing, social care, NHS and rail in the ballot as "crucial issues that the public care about" (the other four topics to be debated are the Grenfell tragedy, public sector pay, workers’ rights, and growth and investment).

Following the result, former shadow health secretary Heidi Alexander tweeted: "I am gobsmacked. How can @uklabou not have a full & proper debate on Brexit policy at #lab17? We will be a laughing stock." Former shadow business secretary Chuka Umunna said: "The party should “not be ducking this debate, we should be leading it”. And Progress chair Alison McGovern told a rally: "I am gutted that our debate didn’t get through. I worry this it’s going to mean that our party isn’t going to be able to consider the biggest issue facing us for a generation."

The outcome shows that Corbyn is now the master of his party, with a degree of power that Tony Blair would have been proud of. Though Labour has not ruled out backing permanent single market membership (rather than merely for a "transition period), Corbyn yesterday told The Andrew Marr Show: "We need to look very carefully at the terms of any trade relationship because at the moment we're part of the single market, obviously, that has within it restrictions on state aid and state spending, that has pressures on it through the European Union to privatise rail, for example, and other services." Corbyn, who voted against the single market's creation in 1986, has long spoken of its existence as an obstacle to socialism.