The sun was out on Friday, and protestors opposed to Donald Trump’s visit had a wonderful time.

There was a carnival atmosphere as the great Trump “blimp” rose into the sky near the House of Commons. There was no chance of President Trump seeing the thing in person, but he might see photos when his staff brief him on press coverage of his trip to the UK.

He won’t care. Asked on Thursday about the planned protests, he blithely insisted that everyone in the UK loves him. In particular, he said, they agree with him on immigration.

Some people probably do, but on balance it seems Mr Trump isn’t as popular as he believes.

One opinion poll by YouGov found only 17% of Brits have a favourable view of President Trump, while 77% had an unfavourable view.

But the protestors were happy and Donald Trump was happy. Spare a thought for the one person who has nothing to smile about - Theresa May.

Prime Minister Theresa May greets U.S. President Donald Trump at Chequers on July 13, 2018 in Aylesbury, England.

She’s been doing her best to square an impossible circle.

Businesses, including major employers such as Jaguar Land Rover, have been crying out for a Brexit deal that allows them to continue trading with the EU pretty much as they do now.

And it’s hard to argue with that. Even the staunchest Brexiteer wants trade with the EU to continue, or so it appears.

During the referendum campaign, they insisted that Germany would be desperate to sign a trade deal with us. Nobody argued it would be a good thing for trade to grind to a halt.

The trouble for Mrs May is that keeping the same total, unrestricted access to the EU’s markets that we currently enjoy means continuing to obey the EU’s rules (which we helped to make, of course).

There’s no way round that. It’s just a fact, however annoying it is.

So her proposed EU deal, agreed at Chequers on July 6 and published in a White Paper on Thursday, is basically about sticking with EU rules while pretending we’re not.

Demonstrators raise a six meter high effigy of Donald Trump, being dubbed the 'Trump Baby', in Parliament Square in protest against the U.S. President's current visit to the United Kingdom on July 13, 2018 in London.

It didn’t fool the Brexiteers. Former Brexit Secretary David Davis and former Foreign Secretary Boris Johnson both resigned.

And then Donald Trump decided to stick the knife in.

Mrs May’s approach was “very unfortunate”, he said. Her proposals for Brexit are “not the deal that was in the referendum”. And they would “probably kill” a US-UK trade deal.

He came to London and handed ammunition to the Prime Minister’s enemies. Then he enjoyed a round of golf in Scotland.

For Mrs May, the chances of delivering a Brexit acceptable to her party, and to Parliament as a whole, are now even more remote.