Here is another bump in the Brexit road that Theresa May will survive

The Prime Minister may be defeated in the House of Commons on the EU customs union, but she will carry on and shows no sign of having had enough

As long as the Democratic Unionist Party prefers May to Corbyn as prime minister, she is safe (PA)

It seems only yesterday that most journalists thought Theresa May was at a low ebb. She is not enjoying it, they said. Her husband Philip must be suggesting they retire to the quiet life. She cannot want to go on.

They are not saying that now. Sometimes what is not happening in politics is more important than what is. It was notable that Jeremy Corbyn finally lived up to the job description of Leader of the Opposition on Wednesday, asking six crisp questions about Brexit. But what was more important was that Theresa May, although she failed to answer them, just made her “Am I bovvered?” face.

It was notable that the Cabinet committee agreed on something at Chequers on Thursday, although no one knows what it was and the EU has already rejected it as “pure illusion”. But what was more important was that neither Boris Johnson nor Philip Hammond resigned.

I won’t say that the Prime Minister knows what she is doing. I don’t want to stretch the bounds of your credulity. But surviving week by week is one of the things she is good at, and if you want me to make a reckless prediction it is that she will secure some kind of deal with the EU and will still be in office when we leave next year.

The next problem she faces is a likely defeat in the House of Commons over a customs union with the EU. We don’t need to go into the technicalities, but she has ruled out a customs union because it would mean accepting the EU’s Common External Tariff, and prevent the UK negotiating its own trade deals on the goods covered by it.

Now Anna Soubry, the Tory Remainer, has tabled an amendment to the Trade Bill which instructs the Government to “implement an international trade agreement which enables the UK to participate after exit day in a customs union with the EU”.

Jeremy Corbyn is likely to support it, although he may not say so in his Brexit speech on Monday. His policy is “evolving”, said Owen Smith, shadow secretary of state for worrying about the Irish border. John McDonnell, Shadow Chancellor, said on Thursday a customs union could be a way for Britain to take advantage of trade terms negotiated by the EU, and could allow Britain to “influence” those terms.

With defeat looming, Theresa May has postponed the Bill, but it will have to be voted on soon. As you can see from the wording, the amendment does not require a customs union. Indeed, it cannot, because Parliament cannot negotiate with the EU, but a vote for it would be a clear expression of the majority for a soft Brexit in the Commons.

So it would be embarrassing to lose the vote, but May has already lost her majority and yet she carries on. Ignore the heated speculation about the Government falling or another early election. As long as the Democratic Unionist Party prefers her to Corbyn as prime minister, she is safe.

She cannot be forced by a parliamentary vote to seek a customs union. If she returns from her negotiations with what she wants, a more limited “customs partnership” that would allow Britain to sign trade deals around the world, Parliament would face a choice between accepting it or leaving the EU without a deal at all.

However, the EU has said it won’t accept what May wants, so if Parliament can’t make her go for a customs union, perhaps Angela Merkel will. And if May decides that would be better than a plain trade deal like Canada’s, it would be a humiliating retreat and the Brexiteers would kick up a fuss, but I think that she would just plough on.

This is a negotiation. For a deal to be done, both sides are going to have to yield. On the UK side, it seems a customs union is a more likely concession than, say, accepting free movement of people or the jurisdiction of the European Court. Public opinion is not greatly exercised by Liam Fox’s right to sign trade deals around the world, and the McDonnell argument for trying to benefit from the deals the EU has already signed is a persuasive one.

What was surprising about the Chequers meeting was that there was hardly any discussion of customs at all – or of its most acute practical form, the Irish border. And I do not think that was because May has a secret plan. All we can do, therefore, is try to guess which way events, personalities and realities will push her.

Charles Grant of the Centre for European Reform, who talks to continental Europeans, says “the EU would welcome a British decision to ask for a customs union”. If that is what it takes to get a deal, then I think Theresa May will do it. Just because she ruled it out – like last year’s early election – doesn’t mean it’s not going to happen.