Donald Trump gives May's Brexit plan both barrels

We all know what it's like - having to play nice with the person you don't have very much in common with, because it's the right thing to do.

Knowing that lots of people you DO like would be upset if you don't put on a show.

Well, how about this: having to "play nice" publicly with a person you don't have very much in common with, when they have said that the way you are trying to do your job doesn't really work.

Add in the embarrassment if they happen to be the leader of the free world.

• LIVE: Latest updates on Donald Trump's UK visit

From the moment of his election, Donald Trump was an awkward friend for Theresa May.

He runs towards a fight. She does everything in public to avoid one.

Well, just before they were due to appear alongside each other on UK soil he publicly, and at length, gave a "both barrels" verdict on her most important policy.

'Driving a bulldozer'

Her approach to Brexit has been to slowly, gently, incrementally, carry the Ming vase across one side of the room to another on a slippery floor.

To talk about being pragmatic, to smooth over the contradictions, to do whatever it takes to get to the other side, without smashing that vase (her party and the country) to bits.

In walks President Trump, to call out one of the claims that No 10 has been making of late - in essence, smashing the vase to bits.

In an interview with The Sun, he shoots down the chances of a trade deal with the US if she sticks to her carefully crafted compromise Brexit plan.

The black tie event was held on the first day of President Trump's visit

That matters because the government has been clinging to the idea of trade deals with countries outside the EU as one of the benefits of Brexit, and claiming that the choice in the Chequers deal to stay close to the EU doesn't exclude those opportunities.

This isn't about what side anyone was on in the referendum. In fact, Remainers and Leavers unite in saying the Chequers deal can't live up to all it claims.

For former Remainers, it's nuts to think that trade deals with non-EU countries can ever make up for what might be lost.

For some Leavers, it's nuts to claim we can make the most of the world outside if we are still sticking to EU rules.

And President Trump drives a bulldozer through the government's central claims about its compromise - that the UK would be able to get decent trade deals with the wider world, while sticking to the EU rules.

A lot of this visit has been carefully choreographed, as the prime minister and the president dance around each other.

But if the president really wanted to help her build support for her controversial compromise, this isn't the way to do it.