REJOICE! A blessed event is at hand. No, not some royal wedding. After 20 months in gestation, the SNP’s Growth Commission is finally due to deliver its report next week. Get the cigars and champagne ready for Friday.

To recap, the Commission was set up by Nicola Sturgeon in September 2016 to “explore options to grow Scotland’s economy in the wake of the EU referendum and consider how to generate further growth with the powers of independence”.

Its 14-member panel was chaired by Andrew Wilson, a former SNP MSP, and included the finance secretary Derek Mackay, business people and academics.

The First Minister was clear it would take on the big trust issues that bedevilled the Yes campaign in 2014, with policies on growing the economy, cutting Scotland’s deficit and “monetary arrangements”, ie currency. Insiders say it will make firm recommendations on them all, not hide behind menus of options.

To old Holyrood hands, the timing rings an alarm bell. SNP HQ, who have had the 400-page opus for months, plan to release it the day after First Minister’s Questions. It means Ms Sturgeon will be able to deflect questions on Thursday with a wave of the hand and a ‘let’s wait till tomorrow’. By the time the next FMQs rolls round, another hot topic may well have supplanted it.

The SNP has reason to be jittery. The report deals with the biggest holes in the 2013 White Paper for independence, which Ms Sturgeon launched jointly with Alex Salmond.

Unionist parties will cite any new thinking as evidence the SNP played fast and loose in the last referendum, spinning voters a yarn about second oil booms and the like, and therefore cannot be trusted in any future vote.

So the SNP will plan for a rocky reception. They may direct people to the exhaustive peer review process the Growth Commission undertook, or say Brexit has forced a rethink, or even hold their hands up and admit they were over-optimistic about oil revenue and presuming to share the pound with an unwilling partner.

They could also draw a line under Salmond era blarney about an easy shift to a super-abundant state and adopt a more realistic, evidence-based tone. Voters have seen the complexity of Brexit. Cheeky patter and breezy assurances won’t cut it.

I think the Commission has other, less obvious problems to face, too. When Mr Wilson became chair, he said he wanted to make a new case for independence. “It is my sincere hope that should Scotland be asked to choose again on independence, this project ensures that we all have as sound, transparent and firm a prospectus has any country facing such a choice has ever had.”

But the SNP is in a different place compared to September 2016. Its members are more independent of mind. The party, like the wider Yes movement, is split over the timing of a second referendum, with some wanting a push before 2021, and others advocating a longer game.

In the absence of any clear direction from Ms Sturgeon - and a fear the party hierarchy is slipping into paralysis on the issue - the former group are taking matters into their own hands, organising local Yes groups and marching in their thousands. I doubt they are in the mood to accept tablets of stone handed down by Mr Wilson.

Indeed, the SNP is currently updating its policy-making apparatus to give members greater input. Reflecting its membership explosion, but also its seized up policy machinery, the party ran an internal consultation earlier this year about overhauling its constitution for the first time since 2004. The results of the exercise will be put to delegates at the SNP’s conference early next month. They include far more scope for members to shape policy, including online.

The conference will also see the new depute leader named. Although the contest between councillor Chris McEleny, activist Julie Hepburn and Economy Secretary Keith Brown has been dominated by differences over referendum timing, all three have promised members a greater say in policy.

“The policy platform will be refreshed; members will be pivotal to building the vision for Scotland after independence,” as Mr Brown, the frontrunner, put it yesterday.

If that process is to be meaningful, SNP members must surely get a say on the policy areas at the heart of the Growth Commission - economy, public finances and currency.

So it’s not clear what status the Growth Commission report will have when it finally appears. Firm prospectus for independence? Springboard for a wider policy debate? Anachronistic doodle?

Because it carries Ms Sturgeon’s imprimatur, it will be impossible to ignore. But because it doesn’t have the membership’s stamp, it will also be hard to assess its durability.

If SNP HQ tried to press it on the grassroots, it would risk a backlash adding to the referendum tensions.

I still expect the report to be interesting in its own right. Those involved describe a serious and thorough piece of work.

But it will also interesting for the light it throws on the increasingly choppy currents inside the SNP.

As delegates react to the report, choose a new deputy, reform their constitution, and ponder the date of a referendum, it could be the most turbulent conference in years.