Despite the rise of nationalism, Scottish politics in 2010 could still resemble old and familiar patterns. I remember the response that Labour canvassers got in a council estate on the outskirts of Coatbridge, a constituency that the sitting MP, a 69-year-old local man, Tom Clarke, had every expectation of winning for the eighth time.

Despite every dismal thing that had happened to Coatbridge, where any prospect of prosperity vanished with most of the iron industry in the 1930s, Clarke’s door-knockers generally got a friendly welcome. Perhaps faith had something to do with it. “He’s a fine Christian gentleman,” said an elderly woman, suggesting that she and he both belonged to the Catholic community that Irish immigration in the 19th century had established as a strong presence in the smelters, rolling mills and mines of North Lanarkshire. In 2010, the Catholic vote may have begun to fracture and fragment, but Labour could still count on it to form a core of support that had its more secular foundations in Labour’s ancestral promise, often fulfilled, to provide working-class voters with decent houses, hospitals and schools. With 42% of the Scottish vote, Labour won 41 out of a total of 59 seats in Scotland that year. Nine years later, in this month’s general election, it won one seat, with 18.6 % of the vote. It was Labour’s lowest share of the Scottish vote since 1910, when in another December election it increased the number of its MPs in Scotland from two to three: the first baby steps in a long and uneven rise to 40 years of late-20th-century dominance when Tory competition died away and the full threat of the Scottish National party had still to be felt. What had taken 50 years to achieve had been wiped away in 10 – or even in five, because in the 2015 election, too, only one Scottish constituency returned a Labour MP.

Such a complete rout for Labour in 2019 – and such a calamity for unionism – had not been easy to foresee. If anything, the portents in the 2010 election had pointed slightly in the other direction. Gordon Brown, whatever his troubles south of the border, was a name that met a mainly agreeable response on the doorstep. Labour had been 13 years in power, but its vote in Scotland actually went up by 2.5 percentage points. The SNP had managed only six seats – the same as five years earlier – but the arrival of the Cameron-Clegg coalition in Westminster and the start of austerity meant that an old, pre-devolutionary argument could be resurrected: Scotland had a government – and government policies – that it hadn’t voted for. In 2011, the SNP won an outright majority at Holyrood for the first time with a manifesto that, among other things, recommitted the party to a referendum on independence.

The riots in London (and in a few other English cities, on a smaller scale) erupted later the same summer.

Alex Salmond, then Scotland’s first minister, complained about the needless damage to the tourist industry caused by broadcasters describing the disturbances as “UK riots” when they were confined entirely to England. His unionist critics accused him, quite rightly, of “gloating” and cheap point-scoring, but other people in Scotland had a different reaction. His remarks confirmed a suspicion that England was becoming problematic in an entirely new way: not as the cause of nationalist anger and grievance but as a troubled society to feel sorry for and be separated from.

This pitying, uncomprehending view of England spread quickly throughout the world after the EU referendum result in 2016, not least in England itself. But it was on a Hebridean island in 2011 that I first noticed that the traditional nationalist position on the union – that it was oppressive – had been changed to the subtler question of what good it did. Economics and public finance apart – an admittedly large exclusion – the question became harder and harder to answer after 2016. It was, my late Scottish colleague Deborah Orr observed, “like being tied to a man wearing a suicide vest”.

In 2014 this future was unknowable. Labour campaigned against independence in the Scottish referendum basically on the grounds that the working class on both sides of the border had a common history and shared objectives: class, then, rather than nation. As Douglas Alexander, then the cleverest of the post-Blair-Brown generation of Scottish MPs, told me at the time, referring ironically to “the inherently progressive quality” of the Scottish aristocracy: “The reason we have a national health service is not because of … the Duke of Argyll, [but] because a Welshman, Aneurin Bevan, secured the votes of working people across these islands in the cause of a progressive ideal.”

This was true, but it ignored the uncomfortable fact that the duke and Alexander were now on the same, unionist side; and that the SNP, particularly its deputy leader, Nicola Sturgeon, now framed independence as the most pragmatic route to social justice rather than the best means of preserving and encouraging national identity. No longer could it be labelled a party of “Tartan Tories”. Labour support among the urban underprivileged, particularly in the party’s old strongholds in the western Lowlands, such as Coatbridge, began to collapse.

That the unionists won the referendum was little thanks to places such as these, each with their equivalents, just as brimming with disenchantment, in the English Midlands, south Wales and the English north. David Cameron’s too-quick reaction to victory, promising counterbalancing English reforms to those the unionist side had promised Scotland, had its consequences in the SNP’s near total victory – 56 seats out of 59 – in the general election of 2015. But how was deindustrialised England to find its cure or get its revenge? The answer came soon enough, in the form of Brexit and Nigel Farage. In 2014, Alexander had rooted the appeal of both Salmond and Farage in their easy blame of “the other” – Brussels in Farage’s case, and London/austerity/the Tories/Westminster (“choose your descriptor,” said Alexander) in Salmond’s.

Another similarity, not easily predicted, was how the fantastical version of English history embraced by English nationalism would equal and then overtake the Caledonian delusions that the SNP was beginning to shed. It had lain dormant inside the fog of British history since Empire Day was last celebrated, but now sprang angrily to life. There had been claymores in the north; there would be Spitfires in the south.

The feeling of Britishness began to wither in many of us during this decade, though unionism, its constitutional cousin, should never be written off. The obstacles to Scotland’s success as an independent state, inside the EU but outside the customs border of what remains of the UK, are forbidding, and nationalists tend towards the non-arguments of Brexiteers when confronted with them (“Oh, it’ll work somehow, you’ll see”). The principal friend of the union is exhaustion.

• Ian Jack is a Guardian columnist