No one decent wants to watch a trapped animal endless in agony. So it was a relief this morning to find the prime minister relishing the sort of mischievous delight to which she’s been a stranger since she ran through a field of wheat.

If only for a couple of seconds, the pulverising stresses of her situation melted away as she revealed to Andrew Marr that Donald Trump’s advice, in the vexatious matter of Brexit, was to sue the EU.

For all its mesmerisingly imbecility, we probably should have guessed. Litigation has been such a reflex response to the thwarting of his will for so long that his unofficial signature tune is Johnny Cash’s “A Boy Named Sue”.

And on that bombshell, the comic portion of Trump’s diplomatic tour ended. In a few frantic days, he insulted May about Brexit, pushed Boris Johnson’s outlandish claim to replace her; insulted the leaders of Nato states about low defence spending; praised the Queen as beautiful “inside and out” during an outpouring of gibberish to Piers Morgan; claimed that many protesters gathered at his golf course were protesting for him ... and far too much more to be catalogued in such a limited space.

It was an absolute blast, and we thank the Prez for the memories from what his fellow golfing legend Nick Faldo would style as the heart of our bottom.

But now it gets serious. Actually, the barely veiled threat to undermine Nato to destruction wasn’t that funny. But tomorrow in Helsinki, it gets really, deadly serious when Trump meets Vladimir Putin.

Not to be melodramatic, but you wonder if this summit might be the starting pistol for the race to dismantle the world order of the last seven decades.

Coming days after Robert Mueller charged a dozen Russian intelligence officers with hacking Democratic emails, the timing is poignant.

“A normal US president” is as stale a phrase as this language can offer right now. But in the wake of such charges, a normal US president would have cancelled the Putin summit (as Congress, politicians and reportedly his advisers have begged him to do).

Tending towards the abnormal, Trump will not acknowledge that the former KGB man had a clue what these agents of the Russian state were up to.

“Every time he sees me, he says, ‘I didn’t do that,’ and I really believe … he means it,” so Trump said last November after they met in Vietnam. “I think he is very insulted by it, which is not a good thing for our country.”

How exceedingly true. This must be why Trump himself takes such obsessive care to spare the delicate feelings of foreign leaders.

Talk of collusion between Russians and Trump associates will no more derail the Finnish love-in, one assumes, than that of alleged kompromat. Trump’s longing to be Putin’s bestie is no mystery. The big question is how far he might go to thaw the neo-Cold War that began after Russia’s invasion of Georgia in 2008 and became more glacial after its annexation of Crimea in 2014.

Will Trump legitimise the latter, and if so could Nato survive in more than name if he does? Will he act on earlier hints about withdrawing the 2,200 US military presence from Syria, in defiance of his entire administration, and end the proxy war with Russia there? Will he consent to do all in his power to relax, or even abandon, the post-Crimea sanctions damaging the Russian economy?

Will he, to boil it down to this simplistic reduction, kickstart the disintegration of this precarious world order by hugging the bear, while recoiling from such close and longstanding US allies as Canada, Germany, France, Mexico and even that gorgeous Majesty’s Britannic realm?

This much seems likely. In a diplomatic game between a skilled and battle hardened chess master and a man without the attention span for checkers, there can only be one winner.

A semi-lobotimised Putin would easily bamboozle the proudest ignoramus who ever sat in the Oval Office. A grifter on a far more elevated scale to the tangerine huckster, Putin needed study his mark for moments to know that, if you’re the kind of strong man he instinctively admires and whose affirmation his insecurities make him crave, flattery gets you everywhere with.

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Trump goes into the summit with a pair of aces in the hole, Putin with a deuce and seven-off suit. But the poker savant’s motto is “play the man, not the cards”, and the supreme bluffer who uses rarefied guerrilla warfare (in Syria and cyberspace) to punch way above Russia’s middling economic weight will surely be too good for a man too effortlessly brilliant in his own estimation to read the first page of a brief.

If it took Kim Jong-un an hour to blandish Trump into handing him the unlikeliest diplomatic coup de théâtre in decades, how hard could it be for Putin to coax him into generous concessions?

In a time of such extreme volatility, nothing is predictable. It would be insanely arrogant to dismiss the possibility that a Russo-American alliance would make the world a safer place on nuclear and other grounds.

But the stronger possibility is that Putin may be a day or two away from schmoozing Trump into threatening the western democratic world order, with a hiding from which it would struggle to recover long after he has gone.