How effective will Dominic Raab be as Theresa May's human shield?

Theresa May has appointed Dominic Raab as the new Brexit Secretary. Credit: PA

The appointment of Dominic Raab as Brexit Secretary to replace David Davis is very smart politics by the Prime Minister.

He is regarded by the True Brexiters as one of them.

In fact, David Davis sees Raab as his protege.

For what its worth, his promotion shows the influence in Downing Street of the director of communications, Robbie Gibb - late of the BBC - in that Gibb has been a fan of Raab's for some time.

If there is a mystery, it is why Raab took the job.

The point is that it is pretty unlikely that he fundamentally disagrees with Davis that May's plan to take EU rules for how we produce goods and food represents a breach of what the British people thought they were voting for in the referendum.

And Raab too is bound to have reservations about collecting tariffs for the EU, since that is likely to see the EU insisting the European Court of Justice has an oversight role there.

So it is too early to say whether he will succeed in persuading Brexiter MPs that they can trust him to deliver a Brexit worth the name, and that they don't have to bundle Theresa May out the door.

David Davis resigned as he does not support the Government's Brexit plan. Credit: PA

As for Davis, he insists he wants Theresa May to remain in office.

When I interviewed him on Monday, he walked the difficult tightrope between making clear his principled opposition to her Brexit proposals, while trying to be loyal to her.

Strikingly, it was only really on Sunday morning that Davis became resolved to go, and then, after a day at Silverstone, he had an early evening chat with the same Gibb and also the chief whip Julian Smith - who tried very hard to talk him back from the ledge.

They failed.

So Davis returns to his habitual role of being a professional pain-in-the-bum to prime ministers of all shades and affiliations - including the present one.