IF the event had been an artistic launch, this would have been just the prologue. A preface, a prelude, a preamble. At most, overture and beginners.

The Presiding Officer, Alison Johnstone, complained that Nicola Sturgeon and Patrick Harvie held a Bute House news conference, rather than first advising Holyrood.

However, I think the staging was appropriate, given the content. There was very little here that shifted Parliamentary discourse.

Rather, it was a restatement of ambition by the SNP and the Greens to achieve independence. Nicola Sturgeon called it a “refreshed” vision.

The Parliamentary content will come when the First Minister discloses to MSPs how she intends to surmount the obstacle that the constitution is reserved to Westminster and that, consequently, Holyrood would appear to be prevented in statute from holding a referendum on its own terms.

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That does not mean that the initiative this week was futile. It had three primary objectives.

One, to continue promulgating the case for an independent Scotland. Nicola Sturgeon yearns to end the Union. Her ambition is neither tactical nor a bargaining chip. She wants independence.

As does Patrick Harvie – although, in his case, environmental concerns tend to rank first.

Two, Nicola Sturgeon needs to placate the more zealous and thus restless elements of her movement. She requires to show progress, even if slightly illusory.

Three, both leaders are seeking to pick a fight with the UK Government. To tempt Boris Johnson to address both referendum process and the substance of independence.

I am struck by the tone of this week’s endeavour. Both the news conference and, in particular, the published document: the first, we are told, in a series which will include such matters as currency, pensions, welfare, the EU and defence.

To some extent, it could be said that the refreshed prospectus builds upon the White Paper published ahead of the 2014 referendum.

However, it strikes me that, initially, it owes rather more to the 2018 report of the Sustainable Growth Commission, set up by the SNP and headed by Andrew Wilson.

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As with the Wilson document, the new Scottish Government paper draws comparisons with small European nations, stressing that each is wealthier and fairer than the UK.

However, the new document inherits another aspect of the Wilson report: caution and caveats.

It stresses that independence in itself “does not guarantee success for any country”. It warns that Scotland would not be able instantly to plug the gap between our economic performance and that of, say, Norway or Ireland.

Further, and most significantly, it notes that future economic performance derives largely from government policy choices while stressing that there is no single route to success: citing, for example, different tax and spending policies across the comparator countries.

That last point could prise apart the SNP and the Greens who differ over whether economic growth is a valid objective: that issue being explicitly excluded from their partnership agreement.

However, the two leaders sought to turn their differences to advantage at the news conference, stressing that independence would liberate people in Scotland to make their own choices.

The question posed by the leaders is that, if countries like Switzerland and Austria can thrive, then “why not Scotland?” Plainly, those words are on their way to becoming a slogan, posed directly to the PM by the SNP’s Ian Blackford.

It is a slogan which is potentially both plaintive and querulous; in itself, rather Scottish. However, if deployed sparingly, it could be effective, provided it works its way into the popular psyche.

More, though, on those caveats. No more reliance upon North Sea oil, despite interrogation from a cross-party grouping, assembled by former SNP Minister Fergus Ewing.

Plus a frank concession that there could be “challenges” for trade crossing the Border from EU Scotland into Brexit England.

In retaliation, Nicola Sturgeon also cited Brexit as an example of a decision taken against Scotland’s will and interests. Yes, there would be challenges – but the benefits would “far outweigh” them.

Will the “refreshed” version minimise discontent in the SNP? Possibly, if they can see signs of energy at the top although again, to be frank, there is little of substance that is new.

However, perhaps novelty is chimerical in this long-running argument, the fault line in Scottish politics. Perhaps the battleplan is too familiar, on both sides.

Which brings me to point three. Engaging the Tories. The initial response was one of studied disdain.

Challenged in the Commons, the Prime Minister deliberately listed other issues which were, in his view, more important.

At Holyrood, Douglas Ross, the Scottish Tory leader, described the referendum as a distraction from key problems such as the NHS and drugs deaths.

In response, the First Minister said independence was the answer, not a distraction. She characterised Mr Ross as “terrified” of the outcome.

What about process? Will a referendum be held in October 2023, as Angus Robertson predicts?

The UK Government says its position is unchanged. That would be a No. Previous subterranean mutterings about imposing possible conditions on a ballot have vanished entirely. In truth, they were always rather ephemeral.

Nicola Sturgeon says she has an “indisputable” mandate to hold a poll and intends to honour that. Presumably, she intends to announce plans for a Holyrood Bill, inviting a court challenge.

I believe she has a fundamental problem here. The SNP manifesto for the 2021 Holyrood elections said: “We are seeking your permission at this election for an independence referendum to be held after Covid.”

Yes, she gained permission, in cohort with the Greens. But a court might say the Scottish Parliament does not have power over the constitution – thus invalidating the mandate.

Which, presumably, is why the manifesto talks of “permission” and not of explicit plans to initiate such a referendum.

It would be possible for Holyrood to hold a consultative plebiscite. But the Tories, for one, say they would boycott that. And, as Nicola Sturgeon acknowledges, independence could only follow a globally accepted ballot.

Remember, though, the primary purpose of this week’s initiative. To revive the issue. To engender debate. This is just the prologue. Act One and more to follow.