In an age when the cult of youth has never mattered more or swept more away, I remain an unrepentant and unfashionable believer in the wisdom of grannies.

I struggle to think of any of the simple truths my grandmother taught me which don’t hold true today.

John Swinney appears to be a man rather careless of well-established truths. Here’s some he could have learned from my grandmother Suzanna: if there’s no need to speak, shut up; and never pick a fight unnecessarily, but once you’re in one don't quit.

Swinney appears more attuned to our age of idiocy. Not for him, the wisdom of grannies.

He’s walked into a fine trap of his own making. He fashioned the snare, laid it upon the ground, and clod-hopped into it, hoisting himself into the air to dangle there like, well, an ass, frankly. There’s no subtler way to put it.

Swinney has got himself into an awkward war of words with Donald Trump. That’s not the smartest move in the world, particularly if you then have to eat a tasty dish of humble pie because your mouth took you too far.

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It’s a sorry tale, for which much patient endurance is needed, but here’s how it unfolds. It began when Trump spoke on a podcast - or rather Trump was moving his lips and words came out. To call that "speaking’" given the man in question, is somewhat a stretch.

The issue of Trump’s Scottish ancestry arose. “My mother was great. She was a Stornaway.” See what I mean about "speaking"?

The master of the mental meander then reflected on Scottish independence. “They tried to break up Scotland from the rest of the empire,” he said, as listeners pictured Redcoats marching down the M8. “I hope it stays together,” Trump added.

"So what," I hear millions of Scots cry in unison, whether Yes or No. It really was a case of "strange man says something, who really cares?".

Swinney, though, cared enough to craft his own Swinney-trap. When asked by journalists about Trump’s comments, he said Americans “should vote for Kamala Harris”.

Now, Swinney had a choice. He could have ducked the question, as most politicians would have, citing a desire not to interfere in foreign elections. Remember what wise old grannies say: don’t pick a fight unless you need to, John.

However, once he was in the fight - of his own making - I, for one, would have retained respect for Swinney if he’d stuck to his guns. Remember the second rule of Granny Club: when in a fight, never give in.

Swinney, however, was soon giving in. Trump won so Swinney sent him a little letter of congratulations. “I wish you every success in your new role,” the First Minister wrote. This isn’t "speaking your truth", it’s speaking with a forked tongue.

Once again, Swinney didn’t need to act. He could have chosen not to write.

He’s not the only twittish politician, though, to come a cropper over Trump. Not long ago, Labour’s David Lammy called Trump a “tyrant” and a “woman-hating, neo-Nazi sympathising sociopath”.

Now, when Lammy said those words I was in full agreement, but then I wasn’t set to become British Foreign Secretary. After Lammy took office, he wasn’t quite so gobby any more. His words were all “old news”. He and Trump shared “common ground”. Trump was “gracious” when they dined together.

Like Swinney, Lammy had two choices, and either would have preserved him from a humiliating public shaming: first, don’t say anything; second, if you’re going to say something, stick to it and don’t prove yourself a back-peddling coward.

Lammy, like Swinney, is an ass. They both wear the donkey’s head, like Bottom - fittingly - in A Midsummer Night’s Dream.

To add to his woes, Swinney now has Team Trump on his tail. Eric Trump - a son - now calls Swinney “nasty” and says it’s “virtually impossible” to do business with Scotland.

Eric Trump rubbed artisan salt in Swinney’s self-inflicted wounds saying the First Minister had read the entire US election “very wrong”. He then raised the issue of tariffs and said of Swinney’s comments: “Does that benefit Scotland?”

So watch out Scotland’s whisky industry.

The behaviour of Swinney - and Lammy - is instructive when it comes to diagnosing what ails modern politics. The answer? Politicians.

David Lammy fell into the same trap as Donald TrumpDavid Lammy fell into the same trap as Donald Trump (Image: PA) Just tell us the truth. If you hate Trump and feel you must say so, then say it - but stick to your bloody guns. If you want to be honest, then be honest and we’ll respect you for it, even if it gets you into trouble with the Trumps of this world.

But to shoot your gob off and then change tune when the big boy turns on you in the playground is a mark of utter cowardice that renders you unfit for office.

People want authenticity in politics - even if they disagree with the authentic words being said. We can see through lies and play-acting. It was the failure to be authentic and honest which led to the rise of populists like Trump in the first place.

Clearly, the opposite course of action is just as valid: old-fashioned, cautious silence. Keep your powder dry until needed. There will be plenty of time to have your say.

Indeed, the public aren’t fools. We already know what the likes of Swinney and Lammy think of Trump without the need for them to say it.

So for whom were these words said: Us? Trump? Or for Swinney and Lammy themselves so they could feel momentarily virtuous?

Evidently, there could be a far dafter reason behind this fandango. Swinney had no cause to comment on the US election at all. He leads a devolved administration, without power on the world stage.

Perhaps he thought some grandstanding would add sheen to the cause of independence. As a Yes voter, however, I’d hazard that running Scotland in a way that doesn’t resemble a child smashing their train-set might be more deft strategically than engaging in a war with Trump.

After all - with a final nod to the wisdom of grannies - we know never to wrestle a pig, as if you do, you both get dirty and the pig enjoys it.

Neil Mackay is the Herald’s Writer at Large. He’s a multi-award-winning investigative journalist, author of both fiction and non-fiction, and a filmmaker and broadcaster. He specialises in intelligence, security, crime, social affairs, cultural commentary, and foreign and domestic politics