I have never knowingly or willingly agreed with Ian Blackford about anything really, but his comments this week made a lot of sense. The focus right now should be on Ukraine, he said, we need to show a united front to Putin, now is not the time for the PM to resign and another independence referendum should only take place when the time is right. Ian, I agree with you.

The only problem for Mr Blackford is that many of his colleagues in the independence movement do not agree with him. Questioned on the same subject, the Scottish minister Patrick Harvie said he had no concerns about holding a referendum next year. In fact, he said it would prove that the UK is a defender of the democratic principles that are being flattened by shells in Ukraine. Patrick, I disagree with you.

The problem here is that the difference of opinion between Messrs Blackford and Harvie is an apparent breach in the SNP wall on the referendum. Almost everyone at the top of the movement is still sticking to the increasingly threadbare idea that there will be a vote next year. But Mr Blackford is one of the first to start to suggest how the SNP will retreat from it. Not that they will admit it’s a retreat of course. It will be another advance, just an advance in a different direction that's all.

Look a bit more at the comments by Mr Harvie and other nationalists, however, and you will see something else: how those who still believe in a 2023 referendum hope to achieve it. “We’re all conscious,” said Mr Harvie, “that there are some in the UK Government who have only one thing to say to Scotland and that is ‘no, you can’t’. I think the more they do that, the more people will feel that their response is going to be to say ‘yes, we will’.”

Mr Harvie may be on to something here I guess: I don’t really believe in national identities (every Scot is different from the next one) but if we do have one, then thrawnness is in there somewhere. Mr Harvie and others also know that Boris Johnson and the Supreme Court will say no to a referendum and hope that the “no” will get our Scottish blood simmering and convert us in bigger numbers to independence.

This, more or less, is the core of the SNP’s plan for getting to a vote in 2023 and independence, but it is not of course their first such plan. In fact, by my count, it is at least the fourth. The first and the most famous – Plan A – was in 2014 and at times it seemed perilously close to success. It did not work out of course, but it was not the end of it, and the SNP’s strategising since then has taken us to where we are now: the beginnings of Plan D.

Before that however, let’s take a moment to remember Plan B, which started in 2017. On the back of the Brexit vote, Nicola Sturgeon announced her intention to hold a second referendum between autumn 2018 and spring 2019. It was definitely, absolutely, no-questions-asked, how-much-you-wanna-bet, going to happen. But then the SNP lost a third of its Westminster seats at the 2017 general election and Ms Sturgeon said she would “re-set” the plans. So much for Plan B.

Then came Plan C. On the back of the pandemic – in the initial stages of which Ms Sturgeon appeared to be doing well – the First Minister announced that her government was restarting work on a prospectus for independence ahead of a new vote by the end of 2023. "Our democratic mandate to allow people to decide the country's future is beyond question,” she said.

However, this time there was already an excuse built in: the referendum, said Ms Sturgeon, would only take place as long as the pandemic had passed. Obviously, this allows for a huge and convenient degree of manoeuvrability – who’s to say when a pandemic has truly passed? You may also think it reveals the First Minister’s true commitment to a referendum in 2023 and that she’s only saying it because she needed to assuage her more restless followers. You’re probably right.

But the problem here is that none of these big events – the election of Boris Johnson, the Brexit vote, the pandemic – have done what the SNP hoped they would, which is to take them to greater and lasting support for independence. In fact, it’s tempting to say that if an annoying English toff forcing Scotland out of the EU can’t boost support for independence, then nothing can.

Which is why the SNP must resort to the only thing it has left: Plan D, which is an attempt to force through a referendum in 2023 by stirring up resentment over the UK government and courts saying no to it, as Mr Harvie was doing the other day. The problem with this plan is that most Scots do not actually seem all that resentful about it. Indeed, recent polling by Savanta ComRes for The Economist showed that only a third of Scots thought it would be wrong for the Supreme Court to decide whether a referendum could go ahead. Maybe we’re not so thrawn after all.

In the end, this distinct lack of anger among Scots about a 2023 vote not happening or being stopped is a serious obstacle to the chances of Plan D succeeding. This is probably why Mr Harvie is busy insisting we are definitely going to be marching up the hill while Mr Blackford is busy suggesting we should get ready to march down it. In private, the leadership of the SNP knows it’s the downhill option that’s likely to happen but even so there was anger in the party that Mr Blackford strayed from the official line which is probably why there was a mischievous leak that he was thinking about quitting as the SNP’s Westminster leader.

The bigger problem, of course, is that when the First Minister does eventually back off from Plan D and the 2023 referendum doesn’t happen, it will be another bit broken off her armour, another piece removed from her reputation. For the moment, she is still insisting it’s full steam ahead, but she said the same about the other referendums that never happened. Her hope, her plan, is that she can ride the anger of Scots all the way to 2023 but my advice is that she should be careful about the kind of anger she stirs up. Most Scots do not seem all that bothered about a lack of referendum in 2023 but the most passionate nationalists will be and it’s what they do that matters. The anger that the SNP seeks to awaken may in the end be turned against them.

Our columns are a platform for writers to express their opinions. They do not necessarily represent the views of The Herald.