Very important breaking news. Which is that trade unions, in their TULO meeting with Jeremy Corbyn, have tonight endorsed the Labour leader's position that in a general election Labour should campaign for a referendum that would have a "credible leave option and remain" on the ballot paper.

The reason this matters is that those senior members of the shadow cabinet, such as Keir Starmer, Emily Thornberry, John McDonnell and Tom Watson, who want Labour to adopt an unambiguous remain position have been defeated.

"It is important that voters who want to leave as well as those who want to remain can vote Labour. What we've rejected is the Trumpian no-deal position of Boris Johnson".

I am told all the unions unanimously backed this position, and that it was not a Len McCluskey and Unite putsch. Watson, Thornberry and Starmer will be devastated, because they fear it will see large number of remain supporting Labour voters switching to support the Lib Dems and the Greens in the looming election.

And it will probably delight Boris Johnson, who would expect to campaign against opposition parties with significantly differing degrees of commitment to reversing the result of the 2016 referendum. But Corbyn has consistently wanted to avoid alienating Labour supporting Brexiters.

A trade union source said: “The union frustration with John McDonnell, Emily Thornberry etc was mainly about timing.

"People know they will push for remain being best even against a so-called improved deal under Labour, but union leaders did not think they should be saying that out loud now."