HE is no diplomat, Alister Jack. The Scotland Secretary can adopt an easy manner and polite and patrician tone in front of the cameras.

But he also has a weakness for properly cringy internet-grade partisan slurs.

Mr Jack let a couple of insults fly this week. At a pretty ill-tempered meeting of Westminster’s Scottish Affairs Committee he had a go at “old Air Miles Angus” Robertson, the SNP cabinet secretary for all things foreign.

The context? The Tory was getting chewed up by SNP MPs over his government’s performative hostility to Scottish para-diplomacy.

UK ministers have been trying to stop their counterparts in Edinburgh hobnobbing with foreigners, at least without a chaperone from Whitehall in tow.

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How come? Tories are vexed that Scottish nationalists talk about Brexit and independence when they are on the road. Which, of course, they often do: it is, after all, their thing.

James Cleverly has put his foot down.

SNPers, the foreign secretary says, should not get help from UK envoys to parlay with foreigners about matters above their station. This bugs Mr Robertson, but also figures outside the SNP.

The admittedly indy-curious Labour former first minister Henry McLeish, one of the architects of devolution, told this paper Mr Jack should “resign” if he could not stand up to Mr Cleverly.

The Scotland Secretary, who has survived three premiers in his post, really is heading for the door. But not till the next election and not because he doesn’t back his cabinet colleague. Quite the opposite.

“I think it is wrong,” Mr Jack told the committee, “for us to facilitate using our embassies for members of devolved administrations to then go and meet foreign government ministers and undermine our foreign policy, which is what they were doing.”

I reckon most foreigners who meet Scottish officials already know that the SNP thinks Brexit is bogging and Indy is braw. And I doubt they will be fazed by talking to sub-state politicians who disagree with “national” governments. Because this is routine.

Mind you, I bet Mr Jack’s patter about “Air Miles Angus” went down well on Union Flag Twitter, which frankly is where it belongs.

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My apologies for reheating this old argument. I only raise it because of something quite remarkable Mr Jack said as he was grilled by the SNP’s Deidre Brock. “We would not talk to Catalan or Corsican separatists,” he told her.

This outburst stopped me in my tracks. This was again Mr Jack using the language of social media warriors, not a cabinet minister at committee.

As it happens, Ms Brock’s response was every bit as gauche. Was the Scotland Secretary, she demanded to know, really comparing the “country” of Scotland with these “areas”? Strewth.

I wonder what the SNP’s allies in Corsica and Catalonia would see as the most offensive: the Tory's pejorative use of ‘separatist” or the nationalist's implication their lands were somehow lesser nations than Scotland.

This dumb, bite-size exchange – maybe as it was always intended – was cut up and posted on social media. Cue more partisan baying.

But all week I keep find myself spinning back to Mr Jack’s assertion that “we” would not talk to Corsican or Catalan “separatists”. Maybe he or Mr Cleverly really would not. Shame on them, if so. But do British officials meet with the autonomist or pro-independence leaders abroad? Of course they do. It would be weird if they did not.

The UK no longer has a permanent presence in Corsica. So its relations with the island’s government – led by moderate “nationalist” Gilles Simeoni – are going to be minimal.

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However, Britain does have a man in Barcelona, a Teesider called Lloyd Milen who, judging by his upbeat Twitter feed, does a cracking job promoting the UK (and Scotland) and transmitting the general bonhomie of a seasoned diplo.

Mr Milen, as you would expect, meets the pro-independence government of Catalonia.

A couple of months back he was pictured shaking the hand of a Meritxell Serret, Catalonia’s still relatively new minister for “foreign action”.

The cheesy official snap was taken in the Palau de la Generalitat, the medieval HQ of Catalan self-government whose stain-glass windows feature the red cross of Saint George – or Sant Jordi.

Behind the British consul were the official flags of both Catalonia, the yellow and orange striped senyera, and Europe. There was nothing Spanish to be seen.

What did they talk about? The current situation – the “actualities” – of Catalonia, among other things.

I am too polite to call Ms Serret a “separatist” but I reckon Mr Jack would.

The 47-year-old independentista was one of the Catalan politicians forced to stay in exile in Belgium in the aftermath of the 2017 independence referendum blocked by Spanish police.

Her meeting with a British official was not unusual. Her president, Pere Aragonès, earlier had a lofty summit with senior Foreign Office officials. They discussed one of the topics Mr Jack and Mr Cleverly say are off limits for Scottish globetrotters: Brexit.

And rightly so: it is in the UK’s interests to have a relationship with – and understanding of – sub-state actors in Europe. Surely that is obvious?

Catalonia has a London embassy or sorts, in one of the only buildings on Fleet Street to survive the Great Fire.

Its current government, like Scotland’s, wants sovereignty but lacks both the political support and the constitutional machinery needed to deliver its aims. But there is nothing unusual about a sub-state government, even one without independence ambitions, having international relations.

The muscular unionists of Westminster want to make a show of opposing the Scottish Government’s embryonic and frankly limited foreign policy reach. Fine, whatever: this posturing will keep parts of their base happy.

But foreign governments – even those hostile to independence – will still want to chit-chat with the SNP-led administration in Edinburgh. Why? Well, for exactly the same reasons that the Brits keep lines of communication open with the people Mr Jack abuses as “separatists”.