There are so many different agendas at play in the Daily Telegraph’s coverage of a brief meeting between SNP leader Nicola Sturgeon and France’s Ambassador, that I need to bring my spin deconstruction skills to the benefit of those trying to make sense of it. Forgive me for the length of this one, but I am doing what Marilyn Monroe ordered in one of her poems …. Think In Ink.

Let’s start with the source. No, not the second level source, namely the UK official who wrote a disputed third hand account, but the primary source, namely the one which brought this to public light, the Daily Telegraph.

The paper is right wing, actively campaigning for a Tory win, and passionately opposed both to Ed Miliband and any threat to the Union. As with its recent story about Tory businessmen supporting the Tories shock horror, served up in a type size normally reserved for nuclear warfare in Thames Ditton, this one is designed as a double hit on two of their enemies – Miliband for daring to want to be a Labour PM, and Sturgeon for wanting a break up of the Union. Oh, and a cursory whack at the French always goes down well.

But of course they would not have had a story to print unless someone had served it up to them, so the question arises, who and how? Margaret Thatcher had a view that you cannot trust a French diplomat, but the current French ambassador, Sylvie Bermann, is on the discreet end of the diplomaytic spectrum, and for the life of me I cannot see any benefit in them being plunged into the kind of debate that has been unleashed. I declare the French innocent of all shenanigans.

Now, dear readers, I take you to the nether regions of the dark arts, and the concept known as MTBL. Memo To Be Leaked. The note of the Sturgeon conversations feels to me like one such. In other words, if there is to be a leak inquiry – generally a waste of time, but the Prime Minister and the Foreign Secretary, cough cough, and the Cabinet Secretary, ought to be worried at the ease with which a sensitive account appears to have reached the public domain – then it needs to start with the diplomat who wrote it and the small number of people who saw it.

My hunch is that it fell before the eyes of a politician or a political adviser who saw the obvious political mileage in having a Scottish leader say that Cameron was more Prime Ministerial than Miliband. The whole Tory campaign is founded on two notions – the economy is recovering (sic), and Dave is a stronger leader than Ed (double sic given the mess he has made of the Union, and Britain’s place in the EU.)

But there is something else at play here, and that is the dangerous game the Tories are playing with the Union. Did anyone else notice how keen George Osborne was to talk up Nicola Sturgeon as he toured the ‘spin room’ after the seven-way debate? The Tories and the SNP have a shared vested interest in the SNP taking swathes of seats from Labour in Scotland. The SNP because it will make them the third biggest party in Westminster, and give them a big say in the governance of the UK. The Tories because Labour are doing better than Osborne expected them to in England and Wales, and they need SNP gains in Scotland to snuff out any chance of a Labour win overall.

So here is my hunch. The the leak was designed to damage Labour and the SNP, in that order. However, because Sturgeon was riding high on the back of a polished performance and she had become something of the woman of the moment, the focus turned much more on her than onLabour.

Now what about the fallout? Sturgeon has adamantly denied the story, and so have the French. However, it is hard to believe that nothing at all was said to justify the colourful account, and also easy to believe that a politician might be a little loose-tongued with a charming and suave French diplomat. It has been known to happen. Oh, and incidentally, there has been less attention given to what reads like a bit of a sideswipe at Alex Salmond and the ‘mischief’ he will cause at Westminster if he gets there after May 7. This is the other layer of political intrigue developing here – they put on a good face together, but Nicola is very wary of the games Alex is likely to play. With reason.

Back to the main plot. What does Sturgeon want from this election? She wants to win. And what does winning mean? It means getting as many MPs as possible. And why? To hold sway. And which party would she rather hold sway over?

Now here I suspect there is a big difference between the public stance seen so clearly from her first answer in the TV debate – ‘I back Ed on the tax rise’ – namely that she sees an alliance with Labour as the best way to lock out the hated Tories; and the private stance about how best to take forward the next step to Scottish independence. That is the ultimate goal of course and nobody should forget that.

So ask yourself, which colour of Westminster government is better able to help her and Salmond pursue those goals? The answer is a blue one. If Cameron is back in Downing Street, he having so screwed up his handling of the referendum on the morning after with his ‘English votes for English laws’ spasm, then any politician, let alone two as skilled as Salmond and Strurgeon, could turn that into the next big step on the route march out of the Union.

A Labour led government, on the other hand, presents more subtle challenges. She claims to be anti austerity. She claims to share Labour’s passion for the NHS. She claims to loathe virtually everything the Tories stand for. So would she bring down a Labour government? Read the history books. They did it before, and the Thatcherism the SNP claims to abhor was the result.

The next TV debate, with five leaders, chicken Cameron having ducked out and forced Nick Clegg to go with him, will have a very different dynamic now. Debate 1 was all about whether Ed Miliband could hold his own as well as Cameron and Clegg, in the face of the public and Jeremy Paxman, and he did. Debate 2 was the only point at which he and Cameron would be on the same stage, so he was right to keep his focus on the Prime Minister, and it was inevitable – as happened with Clegg five years ag0 – that the smaller parties would do disproportionately well from enjoying the same status and platform as the two would-be PMs.

Debate 3 will be about the Labour-SNP dynamic. Just as Nigel Farage did less well than expected because he has been subject to greater scrutiny in recent months, so the increased scrutiny of Sturgeon is now inevitable on the national level. She is a good performer, and an experienced politician.

But even in that seven way debate we could see the openings of her weaknesses. She posed as the enemy of privatisation in the NHS, yet has presided over such private sector involvement when Scotland’s health minister. For all the brio of her verbal assault on austerity, the reality is that if Scotland had become independent, then as a result of the oil price collapse, Scotland would now be in economic trauma. Their calculations were based on more than $130 a barrel; it is now not much above $50. As a result their revenue forecasts are now completely wrong; the balance of payments would be in crisis; and Sturgeon would be negotiating a Scottish currency in circumstances where even a country as rich as Norway has suffered a 35% devaluation of the krone in the last 3 months. So cuts in an independent Scotland would dwarf anything proposed in a Labour Britain, for all her posing as the anti-aausterity champion.

Oh, and could the London media stop talking about Trident as though there is universal Scottish support for getting rid of it? There isn’t. Far from it. It is one of the reasons why – remember – the referendum was ultimately lost by the SNP. At the moment, Sturgeon is riding high on a tide of good pictures and good ratings. Just like Salmond did. But the central choice for the UK, of which Scotland is an important part, is whether a Labour government or a Tory government is better placed to deliver a more progressive future for Britain.

Part of the answer lies in the fact that Tories are giving out a little cheer every time a Scottish poll shows the SNP doing better than Labour. That is worth a thought as May 7 nears. The SNP wants the SNP to batter Labour. And so do the Tories. Only Labour can stop the march to independence. The SNP know it, which is why they need to destroy Labour if they can.

At least independence is an agenda she believes in. Cameron and Osborne are playing a very dangerous game in helping her to pursue a strategy that might help them cling on to power, but which could destroy the Union they claim to believe in.