THE last three years has been a roller-coast ride for the independence movement. We had the great upsurge towards independence in late August and early September 2014, followed by the bitter disappointment of coming so near, yet so far. Then we had the incredible General Election of 2015, which left Scottish Labour almost dead and buried, and the SNP looking like an unstoppable runaway train. And then the slow-down of 2017.

If we have learned anything from the twists and turns of recent politics, not just in Scotland, but across the UK, Europe and the wider world, it is to expect the unexpected. We live in volatile times, and the staid, predictable politics of the past are gone, possibly forever.

But amid the turbulence, one trend stands out with crystal clarity. Politics is deeply polarised, right and left. These days, the centre ground is the most dangerous terrain for any political party or movement to occupy.

Many people feel uncomfortable whenever the issue of social class is raised. They’ll talk freely about other divisive issues – gender inequality, Brexit, racism, independence, sectarianism, war and peace. But class is not a favourite topic for conversation at polite dinner parties. For some people – on both sides of the independence debate – it’s the word that dare not speak its name.

Yet class is a deep faultline that runs right through the heart of society we live in. It was summed up in a Guardian headline this weekend: “Your state pension in Dorset – £124,000. In Glasgow? £38,000.” The point it flagged up was that the average male in the prosperous coastal county in south-west England can expect to live ten years longer than his counterpart in Scotland biggest city.

Yes, one is in England the other in Scotland. But this is about class, not geography. Scotland may have a stronger egalitarian tradition than England, but we live in grossly unequal country. Some of Jock Tamson’s bairns have luxury yachts, lavish mansions and private helicopters, while others have to queue up at foodbanks to stave off hunger. Yes, the independence cause crosses class boundaries. And there’s nothing wrong with that.

Politics is not just about occupation and background, it’s about morality and values.

“Which side are you on?” sang Billy Bragg during the 1984 miners’ strike. That was another time of intense political passion – and there were plenty of affluent professionals, footballers, entertainers, artists and business people who raised money to support the mining communities. And there were also plenty of poorly paid manual workers who believed what they read in The Sun.

I’ve never been a member of the SNP, or the Labour Party for that matter. Unlike some passionate SNP members, I believe that the diversity of the independence movement is one of its greatest strengths. But unlike some passionate non-SNP Yes voters, I believe that diversity won’t deliver independence without a strong SNP as part of the mix.

Right now, the party is caught in a pincer movement. In the rural, wealthier and more conservative constituencies – many of them in the north east – the Tories are resurgent. If that was the only problem the SNP faced, then we could look forward with confidence to the next referendum, whenever that may be.

But the Tories have reached their peak – helped by tactical voting in the Unionist camp – and will struggle in the future to hold onto the gains of 2017. Far more serious is the resurrection of Labour, thanks to a man who was until recently even more hated than Nicola Sturgeon by many of his own politicians and activists in Scotland.

Overnight, hordes of tartan Blairites have been converted to Corbynism. The party that in Scotland denounced universal benefits, boasted of the success of their privatisation programmes, dismissed rail public ownership, built six council houses in the whole of Scotland between 2003 and 2007 and backed Tony Blair’s catastrophic war in Iraq, has now discovered socialism.

It’s like Nigel Farage suddenly demanding that the UK join the eurozone, or Donald Trump appearing at press conference wearing “Refugees Welcome Here” badge.

But voters have short memories and the Labour Party has the luxury of opposition in both Holyrood and Westminster.

Had Corbyn actually won the General Election, rather than run close, the independence cause would, I believe, have been strengthened.

Not because Corbyn is incompetent or unprincipled, but because he would have been left to run a government dealing with the enormity of Brexit, surrounded by hundreds of his own MPs who would be happy to see him fail, and with the whole weight of the establishment ranged against him.

EVEN Clement Attlee, who established the modern NHS, only lasted six years in power, while Harold Wilson’s left wing 1974 manifesto was jettisoned within two years as the IMF stepped in to run the British economy and enforce draconian sending cuts and a pay freeze for public sector workers at a time of rampant inflation.

But it will be a long time before Labour is put to the test at Westminster – and I fear that unless the SNP takes a sharp turn to left and starts to project itself as the party of the Scottish working class, it will lose further ground and weaken the entire independence movement.

Yes, I anticipate disagreement, especially from some of the old guard of SNP activists, who think the party can defy the laws of gravity by standing above such vulgarities as class and left-right politics.

So, in advance, I suggest they peruse the Scottish Social Attitudes surveys of the past few years where they will discover that on a whole range of issues, the people are far to the left of the politicians.

And they will further discover that two in three Scots define themselves as "working class" while just one in four who say they are "middle class".

This is no time for panic, defeatism, or recriminations. On 13 August 2014, TNS published an opinion poll that showed support for independence at 32 per cent. Just over a month later, 45 per cent voted Yes.

We are in stronger position today than we were just a month before the 2014 referendum. But unless we’re prepared to move forward boldly and be part of the radical zeitgeist which took Jeremy Corbyn from back-bench obscurity to the Pyramid stage at Glastonbury, we could be left behind.