Lorna Slater and Patrick Harvie are history makers. Last week’s signing of the Cooperation Agreement with the Scottish Government has ensured that they will forever be the first Green leaders in Scotland (and the UK, for what that may matter to them) to enter government, and with it, presumably, place themselves into ministerial office.

There are few surprises in politics these days. In this era of Trump and Brexit, of referenda and huge electoral swings, there is no such thing as a shock. The announcement earlier this summer, though, that the Scottish Government and the Greens would enter into discussions about a deal based on the moderately binding New Zealand model, raised an eyebrow on me.

Falling short of a majority was undoubtedly a disappointment for the SNP, notwithstanding how clear it was internally that such a feat was going to be exceptionally difficult. However, on 64 seats and with a history from the previous parliamentary session of relatively cheap Green compliance, it seemed unnecessary.

I must say it still does. There is plenty of understandable strategic logic. Firstly, it seems clear that the proximity to which John Swinney came last year to being defenestrated in a confidence vote spooked the SNP government. “The Green Group agrees to support the Scottish Government in votes of confidence” may be paragraph 36 of the agreement, however in priority order I imagine it is in the top two or three.

Secondly, echoing a point made by my fellow broadcast commentator Siobhan Mathers, the climate emergency will require the Scottish Government to make some troublesome and unpopular decisions during this term of office. So why not co-opt a couple of Greens to take the blame?

Thirdly, and I suppose inversely, the eyes of the world are about to be on Scotland as we host COP26, and whilst it is overly simplistic to say it looks good for the SNP to have invited the Greens into government at this point, it does look good for the SNP to have invited the Greens into government at this point.

There is a fourth, more subtle justification. There are many good people in the upper echelons of the SNP who simply want a more mature political discourse and more stable politics, and in a system of proportional representation that generally requires multi-party cooperation. Whilst they might have sought that with Anas Sarwar or Willie Rennie, it is likely that the overbearing constitutional debate would have stifled it. The Greens were probably the only show in town.

But is this logic, and are these benefits, enough? I am far from certain, and indeed, on the face of it the Greens could be the big winners from the deal. I was critical of the Greens’ political nous during the last parliamentary term. They held more mathematical sway then than they do now, yet they consistently failed to extract the potential political advantage available. In truth, the SNP will have regarded Green budget discussions as a fairly straightforward exercise.

The same criticism cannot be made now. To extract two ministerial posts from a party which is only a seat short of a majority is a notable achievement. The positive impact may not be clearly seen until the 2026 election. They have been handed their second vote strategy, and with it the ability to tell SNP list voters that they can elect a continuity nationalist government by voting for the Greens.

They could double, or perhaps triple, their return.

That is not a mortal lock, though. Much could go wrong. Ms Slater and Mr Harvie, should it be they who are chosen, will have to morph into entirely different operators in order to be successful ministers. Mr Harvie, in particular, has been a campaigner, a protestor, for many years; being a government minister will require an injection of pragmatism. It will require them to prevent the pursuit of perfection becoming the enemy of the good, which is effectively lesson one in the day in the life of a minister.

Should this go the wrong way, time in government may expose the Greens and cause electoral harm. It would not be the first time a party has been emaciated as a result of entering a coalition.

The elephant in the room, of course, is independence, and I am quite sure that unionist readers are incredulous that I have taken this long to write the word. However, I am unconvinced that this deal actually has much to do with independence, nor that it moves us any closer to a second independence referendum.

The mathematics do not change; the Greens would always have voted with the Government on the Bill requesting the devolution of the Section 30 power to hold a referendum. The mandate does not change; it is, in my view, already cast-iron, but to those who disagree, the addition of Greens to government will not change their mind.

That is not to say there is no food for thought for the unionist parties as a result of the Cooperation Agreement. Most obviously, if the Greens do benefit electorally in the way I have suggested they might – through significantly more regional list seats – those seats are largely going to be at the expense of the unionist parties (since the SNP has only a handful). Consequently, the super-majority of which people spoke before the last election could conceivably become a reality.

Labour and the Lib Dems may wish to dwell on what might have been. Mr Sarwar, in particular, could have forged a formula relationship of sorts with Nicola Sturgeon, with whom he has a good relationship. In tune with his statesmanlike election strategy, he could have put constitutional politics aside. Although that would have put the Tory Twitter team into hyperdrive, it would actually have been a viable part of a calmer, more considerate and ultimately more successful unionist strategy.

For the Tories, there is a more basic reflection available. They are now the only party in the Scottish Parliament which has never been part of the Scottish Government. More worryingly, they are the only centre-right party in the democratic world, at least that I am aware of, which has no viable route-map to government.

For all that politics is changing, some things remain constant.

Andy Maciver is director of Message Matters.

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