Not so much a press conference as a 50-minute couples counselling session. One in which the therapist was regrettably absent, leaving no one to mediate between two rapidly fragmenting psyches which were almost beyond help. The abuser and the abused.

When Donald Trump described his relationship with Theresa May as “the highest level of special” he was for once telling the truth. It’s just not a level of special to which most normal people aspire. More like pathology unplugged. The rest of us could only sit back in wonder as two of the most powerful people in the world unravelled before our eyes. A collector’s item we will never see the like of again.

If the prime minister had gone into the final leg of the president’s UK tour determined to grab some self respect from her near 48-hour beating, she blew it right at the off. On the walk down through the Chequers garden towards the two wooden lecterns, the Donald had made a grab for her hand. And she had submitted. Yet again a handmaiden. The power relationship had been instantly re-established.

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In her opening remarks, May struggled to recall anything positive that had come out of the visit. They had talked a bit about security and being ambitious for deals and that had been about it. There had been a few tough words – all from one side – because that’s what being in a relationship was all about. Being bullied and shouted at. At this point she looked across to Trump as if for reassurance. The president didn’t appear to notice, as his puffy eyes were closed to a narrow squint by the sun. Where were the sunbed goggles when he needed them?

“Thank you,” said Trump. Everything had been truly magnificent, the truliest magnificent. Even when he’s reading from a script, he manages to sound slightly unhinged. What he had got from the trip had been that it had all been about him. Anyone he’d met had just been satellites orbiting round his ego.

He’d loved his historic buildings tour and it had been a great honour for people to meet him, he’d come “from a productive summit that was truly a productive summit” and whatever Brexit deal Britain did would be fine by him, just so long as it was the kind of deal of which he approved.

So far so not very good, but things really fell apart when some of the assembled hacks got to ask questions. In particular about the interview the president had given to the Sun. May did the only think she knew how. She went into hostage video mode, repeating a few bland remarks about Brexit meaning leaving the EU while looking like someone who was praying for her ordeal to come to an end. Having the Maybot function sometimes has its advantages.

I, Donald Trump, look forward to not meeting anyone in Britain, England Read more

Trump, though, had barely got warmed up. The Sun interview had been lies. “Fake news,” he spat. The things he had said about Theresa being completely hopeless and Britain having no chance of a trade deal with the US were obviously made up because he hadn’t said them after all even though there was tape of him saying them. There was nothing he said that he didn’t reserve the right to later contradict. The US press corps didn’t bat an eyelid on this. The president’s instability has long since been factored in. The Brits couldn’t believe what they were hearing. Or their luck.

It soon got worse. Britain was a terrific place. The terrificest place. Apart from all the immigrants who had come over here. Each and every one of them were potential terrorists and should be locked up. Just as he was doing in the US. It was a fact that America was superior to anything that had happened before.

Then he went into overdrive. Sure, Boris Johnson would make a great prime minister. Why not? He was a great guy who had said some nice things about him. May looked as if she might throw up at that point. It was a while since a prime minister had been publicly insulted in her own back garden. Even when Trump went out of his way to praise her – “She’s doing a great job. The greatest job” – he somehow managed to sound patronising and condescending.

No, he wouldn’t take a question from CNN because they were more fake reporting. But, hell, he knew about nukes because his uncle had been a professor of nukes. He was now full-on delusional, repeating lies about events and meetings that had never happened. A masterclass in uncontrolled narcissism made orange flesh.

May tried to drag him away and get him on the first helicopter out of Chequers but Trump kept dragging his heels. He loved the TV cameras. He needed the attention. It was the only way he knew he was alive. More, more, more. A seemingly endless stream of unconsciousness. Too far gone to notice that he’d reduced the office of president to a third-rate cabaret turn.