Fifty years ago this month, a group of leftwing Scots gathered in the Golden Lion hotel in Stirling for the inaugural conference of a new political party. The “Scottish Labour party” had formally split from Labour at the beginning of 1976, driven by disillusionment over the party’s timid proposals for a new Scottish assembly. They were led by the firebrand MP for South Ayrshire, Jim Sillars, who promised to take Scotland’s Labour tradition back to its roots in both socialism and home rule.

Sillars’ new party was a media sensation in Scotland, and quickly joined by public intellectuals such as Tom Nairn, Hamish Henderson and Neal Ascherson. It offered something new and exciting: a fusion of the two movements that were battling for Scotland’s soul in a decade that had already been defined by electoral clashes between Labour and the Scottish National party.

The party struggled, however, to enthuse the working-class voters on whom Sillars had gambled his future. It did attract a handful of Trotskyist activists from the International Marxist Group, and at the October 1976 conference, Sillars orchestrated a heavy-handed purge of the far left, causing proceedings to degenerate into near-violence. At one point, a member of the party’s national organising committee summoned up Ayrshire’s mining heritage against the “entryist” threat, yelling: “We should get our fucking pit boots on and wade into them!”

Andy Burnham was not quite as forthright earlier this month, when, midway through the SNP’s conference in Aberdeen, he delivered his own speech in Motherwell, offering to cooperate on further devolution within Scotland. The conference itself was far more peaceful, the SNP having already shed its “fundamentalist” wing with the breakaway of Alex Salmond’s Alba party (which Sillars, it’s worth noting, also endorsed).

The National Economic Council meeting on Friday between Burnham, John Swinney and the Welsh first minister, Rhun ap Iorwerth, emphasised the shared agenda of three governments seeking to combine devolved power with reindustrialisation – precisely what the SLP was calling for in 1976. But the SLP, which never recovered from its public meltdown in Stirling, made another contribution to the cause that matters intensely to the relationship between Burnham and the SNP.

Keen to make national self-determination palatable to socialists, Sillars’ party sought to remove any hint of separatism from its politics by embracing the new European Economic Community, arguing for “independence in Europe”. With goods, people and services moving freely across borders, independence would no longer mean separation, but simply real equality between self-governing, co-dependent nations.

After the SLP’s collapse, Sillars found his way into the SNP, rising through the ranks to become deputy leader in 1991. “Independence in Europe” came with him. The SNP made some of its first breakthroughs in the 1970s as a Eurosceptic party, distinguishing itself from the three pro-EEC Westminster parties by campaigning against membership in 1975 with the slogan “No voice, no entry”. But by the 1990s, it had completely reversed this position, helped by the new European Union’s growing emphasis on the rights of small nations and minority cultures.

The SNP’s newfound Europeanism reflected and reinforced that of the country it came to govern. It was helped, too, by Scotland’s tendency to define itself against English politics, which became more Eurosceptic over the same period. When the SNP’s success produced a referendum on independence, Europe was one of the central issues. An independent Scotland, voters were told, would be a new state, and would therefore have to reapply to join the EU. Scots voted against independence partly to protect their European passports. Two years later, they voted overwhelmingly to remain in that larger union too.

But England, with 10 times Scotland’s population, swung the result the other way. Scotland was thus asked, over the period of just two years and two votes, to choose between its membership of the UK and of the EU – but in the wrong order. Immediately after the Brexit vote, support for independence briefly surged, but then dropped. Scots realised they did not fancy yet another wrenching break-up. It was only with the arrival of Boris Johnson as prime minister, the conclusion of a hard Brexit, and the beginning of the Covid-19 pandemic that “yes” moved into a consistent lead.

Today, yes and no are neck and neck, but many independence campaigners remain concerned about how another referendum campaign might unfold. The fundamental political case for independence has always been that British politics is overwhelmingly Anglocentric, and Scotland’s interests are marginalised. While Brexit has deepened this structural complaint, it has also transformed the economic arguments against independence: if Scotland were to vote for independence and rejoin the EU tomorrow, it would suddenly face a hard border with the rest of the UK, which buys more of Scotland’s exports than every other country in the world put together – including the whole EU.

Some nationalists argue that, under such circumstances, Scotland could be granted the same status as Northern Ireland, which has found a middle ground between European and UK markets. But Northern Ireland has been given special treatment because of the simmering threat of a return to open conflict over the partition of Ireland; Scotland is not a remotely serious candidate for civil war over its borders with England or Europe and would be highly unlikely to be treated with the same sensitivity by the global community.

Scottish nationalism’s problem is also its greatest selling point: it is not motivated by any deep ethnic grievance, and as such its supporters are hard to mobilise into the kind of bloody-minded self-sacrifice that might justify some deeper rupture with England. It is founded, instead, on a modern, peaceful and democratic discontent with Westminster’s gradual abandonment of everything that seemed to make Britain worthwhile: good jobs, functioning public services, international cooperation and a vaguely shared moral compass.

Burnham is therefore a meaningful threat to the SNP, for this is precisely the nostalgic vision of Britain that he promises to restore – with messaging skills that can finally rival the SNP’s and promises of “regional empowerment”. Yet it offers an opportunity as well. It is hard to imagine that Burnham, whether he has three years in power or a decade, will truly be able to resurrect the lost world of dignified work, British industry and social security that he conjures up in his speeches. But it looks increasingly plausible that he may have to rebuild some of Britain’s relationships with Europe as a precondition of his wider agenda.

That would repair the one bridge that Scotland truly needs intact for a successful sprint towards independence, should the rest of Burnham’s project falter. Rory Scothorne is a historian and writer based in Edinburgh