A WEEK out from the 2017 General Election, Jeremy Corbyn told me, "We’re gonna do it, you know". Despite the narrowing of the opinion polls, I didn’t really share his confidence – although I didn’t tell him that to his face, muttering something about seeing him in Downing Street.

This particular moment in the campaign was the morning after a round of media interviews the night before in Glasgow’s Old Fruitmarket.

Talking to two reporters from commercial radio, he was asked about the prospect of a second independence referendum.

“I'll obviously open discussions with the government in Scotland and listen very carefully to what the Scottish Parliament says,” he told them.

That wasn’t the line. Far from it.

So, when his comments broke and the Tories jumped for joy, the party had to issue a humiliating "clarification".

It read: “Labour firmly opposes a second independence referendum."

Did Mr Corbyn’s comments damage Scottish Labour’s campaign? Undoubtedly.

The six gains the party made north of the Border in 2017 would have been greater were it not for Mr Corbyn’s failure to adhere to Scottish Labour’s ‘together we’re stronger" election message.

The manifesto he stood on was clear: “Labour opposes a second Scottish independence referendum. It is unwanted and unnecessary, and we will campaign tirelessly to ensure Scotland remains part of the UK.”

And at the launch of the Scottish manifesto, the message was resolute: Labour would never support the break up of the UK. That message, coupled with a strong anti-austerity pitch, was key to those electoral gains.

"Together we’re stronger" not only positioned the party as supportive of the Union, it also neatly fitted with Labour’s proud trade unionist background and vision of solidarity. It cut through.

Its dual purpose was not dissimilar to the SNP’s current slogan, "It’s time to choose our own future", which could apply to independence, Brexit, or both. Take your pick.

Labour’s 2019 message – "It’s time for real change" – is certainly not the worst slogan, and there’s little doubt that yesterday’s flagship policy announcement of free broadband for all amounts to real change.

In fact, south of the Border, Labour is making a decent fist of getting its message through.

Sky News might still be branding it the Brexit Election but – as in 2017 – public services have once again come to the fore.

Figures published this week showing that hospital performance in England is at its worst level on record were a gift for Labour. Boris Johnson is not having it all his own way.

But, on his two-day visit north of the Border, Mr Corbyn expressed frustration at the issues the Scottish media has been asking him about. Journalists who politely questioned him say he was particularly tetchy with them.

Why aren’t you asking me about housing, he demanded to know. Apart from the fact that housing is devolved, of course.

Not that candidates from any party who want to lead a country, in a functioning democracy, get to choose what they’re asked about anyway.

But the reason why Mr Corbyn struggles to cut through with his message in Scotland is because of his lack of clarity on the constitutional question.

His confusion in 2017 was nothing compared to the contortions this week.

Somehow, he managed to produce four different positions on a second independence referendum. In the space of just two days.

First, he kick-started his Scottish tour pledging to rule out another referendum for the entire five years of the next parliament.

If that had been Labour policy from the start, it would have been a reasonable position to promote.

It differs from the harsh version of the Tories’ pledge not to "allow" a contest under any circumstances, and shares more with Theresa May’s softer "now is not the time" mantra.

When only 27 per cent of voters in Scotland support a referendum before 2021, according to one recent poll, there’s a clear argument to be made that a new and radical Labour Government should have a full term to introduce "real change" – and resolve Brexit – before another independence contest is held.

But Mr Corbyn had barely got his words out before his aides briefed that this wasn’t in fact the position. No, they said that opposition would be relaxed if the SNP won a majority in the 2021 Holyrood election.

This all happened on Wednesday morning. By Wednesday afternoon, mere hours later, the party moved on to position number three.

Now the Labour leader had returned to a form of words that ruled out a referendum in the "early years of a Labour Government". No clarity, at that time, on how long these "early years" would last.

And so on to position four on Thursday morning.

Mr Corbyn told the media he would "certainly not" hold a referendum in the first two years of the Government.

This prompted ridicule from the Tories: "Pro-UK supporters in Scotland will be glad Mr Corbyn isn’t staying another day", said Jackson Carlaw.

And from the SNP: "By the end of the week, at this rate, Corbyn will be demanding indyref2020,” joked Nicola Sturgeon.

Mr Corbyn should perhaps be grateful that his opponents still consider him worthy of ridicule, and not just pity.

The Labour leadership would dearly love to be talking about issues other than the constitution.

And Labour activists would dearly love to have a consistent line on the constitution when knocking on doors so they can talk to voters about other issues.

But neither is possible when Mr Corbyn doesn’t have a stable position on the dividing line in Scottish politics.

What is deeply frustrating for so many in Scottish Labour is that the party knew from its 2016 Holyrood result that it had to be clearer on the issue of independence. Only once voters knew where Labour stood would they be willing to listen to what else it could offer.

That lesson was largely learned by 2017, but is now utterly ignored by Mr Corbyn.

Today, what is known as the party’s Clause Five meeting takes place to finalise the election manifesto.

If the last few days are anything to go by, it may also be "take five" when it comes to what the party’s leadership thinks about a second independence referendum.