In Westminster, the assumption has long been that Labour will vote against the government’s anticipated Brexit deal in the autumn. Keir Starmer, the shadow Brexit secretary, has devised “six tests” that any agreement must meet (including delivering the “exact same benefits” as membership of the single market and customs union). Rather like Gordon Brown's “five tests” for euro membership, these appeared deliberately unachievable (both the EU and the UK government have stated that Britain will not retain the “exact same benefits” after the planned transition period).

Earlier this week, Starmer backed an amendment to ensure that the UK would not automatically leave the EU if parliament votes against the deal. And though Jeremy Corbyn, and many of his allies, are life-long Eurosceptics, their desire to bring down the government outweighs their antipathy to Brussels.

But at a Chatham House event earlier today, Emily Thornberry candidly stated that Labour would “probably” back Theresa May’s agreement. She said: “What’s the nature of the divorce? And I think if past evidence of the last few months is anything to go on, it’s going to be a ‘blah, blah, blah’ divorce.

“It’s not going to actually make any decisions, it's going to continue to kick things down the road. We don’t seem to have come to any difficult decisions at the moment.

“The difficulty is going to be with the meaningful vote in October, which we have secured, is that, what is it we are going to be agreeing on? We have our six tests. If you hold up ‘blah, blah, blah’ to the six tests, it will probably pass it."

Is Thornberry right? A Labour source played down her comments: “How we vote on the withdrawal agreement will be decided against our six tests. We won’t know the details until October.” The source added that the EU would not accept a deal as vague as Thornberry suggested.

But the suggestion by Thornberry - one of Labour’s most senior cabinet ministers and a proud Remainer - that the party could back the agreement is significant in itself. A Labour MP told me: “Keir [Starmer] says it's not the position and ‘he is sorting’. People furious with Emily.”

A spokesman for Thornberry said: “Emily made clear, as we have done for more than a year now, that the government needs to deliver a deal which meets our six tests, in particular by explaining how we will maintain current arrangements on the Northern Ireland border, and ensure all UK firms maintain the current benefits of access to the Single Market and Customs Union. We await to see if we will get any substantive answers on those questions by the time of the planned vote in October."

Even if Labour were to vote against the deal, many increasingly believe that it will pass. The EU has consented to a Brexit transition period of 21 months (after the government’s many compromises). And Jeremy Corbyn’s handling of Russia and anti-Semitism has made Conservative MPs even more reluctant to walk through the voting lobby with Labour.

Update: Here's how Chuka Umunna, one of Labour's leading pro-Europeans, has responded (via Open Britain).

“It is extraordinary and unacceptable that the shadow foreign secretary seems to be suggesting that some ‘blah blah’ from the Government will be enough to secure Labour’s support to write the Government a blank cheque for Brexit.

“It’s an old-fashioned idea but it is the job of the opposition to hold the government to account and that is what our members expect to see rather than blasé chat about ‘blah blah’ on the most important issue facing the country.

“The public will rightly take a very dim view of the Labour frontbench joining arm in arm with the likes of Jacob Rees Mogg and other Brextremists to vote for a Brexit which will cost jobs, damage living standards and leave our public services with less investment.”