THIS much I know: man-children are more trouble and less rewarding than the under-age variety. I give you Alexander Boris de Pfeffel Johnson, and Donald John Trump, very visible evidence that age is indeed only a number. Their collective one being 13 going on 14. In a favourable light. (Apologies to well-behaved teenagers everywhere.)

Let us begin with the PM’s latest infantile stunt – sending an unsigned photocopy of a pro forma letter to the EU requiring they consider a Brexit extension – that device which hitherto was going to have him expire in a handy drainage channel.

Then compounding this inelegant two fingers to the Benn Act, by having his EU ambassador attach a cover note explaining they should ignore the first pretendy one. And, lest the recipients be in any doubt that he was in a serious sulk, phoning round European leaders and dispatching a third missive explaining how it was just nasty old Parliament which was doing the asking and he wanted to part of it. Just say no.

This has all the familiar hallmarks of a two-year-old stamping his or her feet, shouting “can’t, shan’t, won’t” at the top of their lungs, prior to ejecting all their toys from their stroller. Two-year-olds who refuse to believe they can’t have their own way and suppose the route to a parental cave-in is to stage a very public strop.

Tomorrow will tell whether the Court of Session in Edinburgh considers this blatant flouting of at least the spirit of the law sufficiently unacceptable to have Mr Johnson spending a lot more time with his lawyers.

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Mr Johnson has much form in considering his will to be paramount regardless of parliamentary legislation or the rule of law in general. Let us remember that having been elected as Tory party leader and accidental PM for fully two minutes, he tried to shut down Parliament altogether. The constitutional niceties were only restored after the intervention of the Scottish and UK supreme courts.

In this lofty disdain for legal and political precedent, he has a transatlantic twin in the American president. “They call Boris Johnson the British Trump,” hollered the orange-tinted one on news of Johnson’s elevation. No we didn’t actually. But we couldn’t help noticing how much they have in common nevertheless.

When Trump won the presidency – despite losing the popular votes by some millions – shocked analysts across the political spectrum comforted themselves with the thought that the US system allowed for checks and balances on the Executive in the form of Congress and the judiciary.

They failed to factor in that Trump had a positively Johnsonian disdain for any such trifles. To their eternal shame, his Republican troops affected not to notice that the election had brought them a narcissistic, bigoted monster with a gossamer thin skin. And a proven, serial liar to boot.

The National: Donald Trump

(Another trait he shares with the boy in Number 10.) Only when Trump casually started a new conflict in the Middle East did some of them remember to notice that their commander in chief was a completely loose cannon without the smallest clue about geopolitical strategies and diplomacy.

And now that the Democrats have formally started inquiries about possible impeachment, the sound and fury emanating from his Twitter account knows no bounds. He has a particularly juvenile habit of attaching scathing adjectives to his political enemies; another weapon of war favoured by the under-10s in the playground.

There are, of course, many differences between the two men. The Prime Minister has a decent grasp of the English language and can speak and write in intelligible sentences. Whereas the presidential outbursts often defy translation even into colloquial American.

But perhaps their most important common quality is one often shared by the rich and powerful: an unshakeable belief in their own sense of entitlement. A notion that the world was put on to facilitate their desires, however base, rather than their having been put on the world to make it in any way better. When that assumption of entitlement operates in tandem with industrial-strength arrogance the result is never pretty.

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It is that overweening arrogance which has led to Johnson’s latest fit of pique; a more experienced, less self-centred politician would have displayed a more nuanced approach to his latest setback. They might have reflected that those Conservatives who supported the Letwin amendment did so because, quite rightly, they believed that anything so profoundly game-changing as a Brexit deal has to be examined in forensic detail, rather than nodded through at the behest of a tyro premier whose word and bond are barely on nodding terms.

And there is something else. As any well-functioning school demonstrates, the community takes its cue and its culture from the top. The crass behaviour of Trump has led not to mass outrage on the part of his Republican colleagues, but, increasingly, a willingness to parrot his lies and insults. He has, almost single-handedly, coarsened public discourse in America.

Similarly, we witnessed in the Commons on Saturday an outbreak of loutish behaviour on the Government benches, culminating in an orchestrated walkout when Joanna Cherry was called to make her point of order.

Apologists for this – led shamefully by Tory Scots – have been at pains to point out that Ian Blackford once led his own troops out the Commons. But he did so on the back of the UK Government attempting to grab back devolved powers post-Brexit with no debate. Hardly comparable to vacating the chamber en masse when a member rises to speak.

These are perilous times both nationally and internationally.

Times which call for statesmen and women capable of rising above the party fray to examine what might most benefit their country. Instead, in both the UK and the USA, we have two men suffering from arrested intellectual development.