After weeks of playing down expectations of an imminent Brexit agreement, Rishi Sunak is now setting the formal wheels in motion to lay out the deal he has struck with the EU.

But there is still a big question about whether he has got the politics of this right on this side of the channel.

A period of inactivity over the last week has given space for Boris Johnson and other Brexiteers to start to agitate against the plan.

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Any rebellion in Westminster could have been neutered by bringing the Democratic Unionist Party (DUP) on side.

But it’s here where the politics looks most precarious for the prime minister.

There are questions about whether the DUP has been kept in the loop – even informally – about talks with the EU.

The story broken by Sky News at the weekend about the aborted plan to involve the King hasn’t helped either.

Has the groundwork really been laid for some of the compromises that will be hard to swallow in Belfast?

One of the biggest mistakes made by Theresa May while she was in No 10 was to assume the negotiation with the EU was the one that would determine whether her Brexit deal was a success.

As a result, focus drifted from the domestic politics meaning the DUP were not brought on board and ultimately her premiership was sunk by her own backbenchers.

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At the time a DUP source briefed the press that “this is a battle of who blinks first, and we’ve cut off our eyelids”.

That about sums up the concrete resolve of a group for whom politics runs a lot deeper than just party allegiance.

Mr Sunak may be about to learn all this the hard way.