A whole year before the independence referendum, Alex Salmond sat down with a sophisticated foreign television journalist and knocked the BBC.

The then first minister, fielding some of the softest questions fired at him over a long, long campaign, was in good form.

The BBC, Mr Salmond said, had an "understandable" challenge covering Scotland. But it was, he argued, failing to do so.

It was a modest enough observation. But it was, I suspect, exactly what his interviewer, Sofiko Shevardnadze, granddaughter of the former Soviet foreign minister, wanted to hear.

Because this interview was on RT, one of the Kremlin's mouthpieces. And there is nothing RT loves more than eroding confidence in western media.

News: SNP shuns Kremlin mouthpieces

HeraldScotland:

The channel's slogan is "Question More". But its aim is to equate Britain's public broadcaster and the UK's free press with its own diet of crude Kremlin propaganda and sometimes subtle trolling of Western institutions.

Thus Mr Salmond became what, back in the simpler times of the Cold War, used to be called a "useful idiot".

These were the crackpots or "progressives" paraded by the old Communist rulers in Moscow whenever they needed a dose of whataboutery to counter Western criticism.

Mr Salmond was not the only useful idiot. Jeremy Corbyn, the Labour leader, was a regular on RT before his election.

HeraldScotland: Jeremy Corbyn

Mr Corbyn even called on his followers to watch the channel, saying it was more "objective" than western media.

I thought this was particularly ironic: RT specifically rejects objectivity as a concept.

Critics refer to the channel as the "Kremlin's Weapon of Mass Deception", part of a sophisticated arsenal, for example, in the hybrid war Russia has waged in Ukraine. It lies and it deceives. It is not normal journalism, however low your opinion of British "hacks".

Both Mr Salmond and Mr Corbyn, I guess, were driven to RT by a "mainstream media bias" narrative long shared by the SNP and the Labour party.

But their distrust of the the dreaded "MSM" has effectively driven them in to the arms of broadcasters that, in my view, have little in common with the kind of free and balanced television that, quibble aside, we enjoy in the UK.

And that is starting to worry very senior people in the SNP, acutely aware of how their party could be exploited by the Kremlin as it "trolls Britain".

Russian state media is actively courting independence supporters.

Or at least it is trying to. Mr Salmond's appearances aside, the party now routinely rejects interview bids from RT and its sister organisations like Sputnik.

HeraldScotland:

Why? The SNP is trying to reassure international partners that an independent Scotland would be a solid western ally. The last thing it wants is to be seen as naive Kremlin stooges.

So what is Russia's game? Well, Mr Putin's government wants to equate our big vote in 2014 with their own referendum in Crimea, the disputed Black Sea peninsula they annexed from Ukraine.

Some Scottish nationalists haven't quite figured this out. Martin Docherty-Hughes MP has. He wants activists to think carefully even before engaging on social media with messages from RT or Sputnik.

After all, under Putin, separatism is a crime at home but a PR opportunity abroad.