As I write this, some of the best-paid brains in Europe are puzzling over what happens when the inevitable suddenly becomes impossible.

For the past half-decade, Greece was run by machine politicians who took orders from their northern European creditors and stamped on their own voters – slashing their pensions, selling their national assets and wrecking their economy. The weekend’s elections put an end to that cosy, monstrous system. And so in banks across the continent, analysts handier with statistical probabilities than political unknowns tweak their models. Ministers and pundits look on the tumult in Athens and wonder how to shape it into a glib one-liner.

Amid such febrility, it’s natural to want to pass the first verdict on Syriza – and completely dishonest to do so this early. The coalition of leftists numbers Maoists and Trotskyists, alongside others who sound more like Roy Hattersley. Rather than soundbites and polling, their expertise is typically in Japanese monetary policy or Lacanian philosophy. Tony Blair’s eager young shavers – glued to their BlackBerrys for the next line from HQ – they are not.

But instead of speculating about Syriza’s future, we should draw one vital lesson from its very recent past – one that Ed Miliband and his inner circle ought to learn too. Because there’s no way that Alexis Tsipras would have been sworn in as prime minister had it not been for the disastrous and ultimately suicidal behaviour of Labour’s sister party in Greece, Pasok. The death of the country’s main centre-left organisation has been swift and spectacular.

Until the financial crisis, any comparison between Pasok and Labour would have left the Brits in the shade. In a small country, it had hundreds of thousands of members, the affiliation of most of the trade unions and an impressive working-class base.

From the early 1980s it was the natural party of government. By last weekend’s polls it was little more than a rounding error, with one of its former prime ministers running against it in a faction of his own.

What happened? Two things that will be familiar to any Labour-watchers. Most immediately, the party accepted Europe’s demands for austerity and imposed massive spending cuts on its own supporters. But over the longer run, it went from a mass movement to an arthritic bureaucracy in the pocket of a small, corrupt elite. Scandals over kickbacks and expenses mounted. One family – the all-important Papandreous – provided three of Pasok’s prime ministers.

Add those two grievances together and you got what I saw in Athens in 2011 as the capital was regularly shut down by strikes and rallies. Outside the Vouli, Syntagma Square was occupied by thousands of people protesting at some of the biggest spending cuts ever seen in a developed country. Pasok’s leader, George Papandreou, couldn’t even speak Greek, you were told by protesters holding placards that labelled him “Goldman Sachs’ employee of the year”. The disconnect was felt just as keenly by the foreign-educated governing elite: one of Pasok’s rising stars was an MP who introduced herself to me saying “I’m not Greek, I’m American”. She was only half-joking.

However painful the cuts faced by Britons, they do not compare to those borne by the Greeks, where national income has shrunk 25% since the banking crisis, 25% of the workforce can’t get a job and 60% of young people are unemployed. But however extreme Greece’s circumstances, it is an outlier rather than an anomaly. And it would take a particular blindness to look at today’s Labour party – home to the descendants of Kinnocks, Benns, Straws and Goulds, as well as a host of sleek former special advisers – and not see in it traces of the same toxic eliteness that killed Pasok.

You can push the comparisons further. Labour rightly attacks the coalition for its economy-capsizing austerity, but then brings out its own programme of massive spending cuts. Pasok saw Greece’s manufacturing base crumble; Labour waited until the crash to bang on about an industrial strategy. Pasok took its vote for granted; there are whole tranches of Britain where Labour assumes the electoral maths will work its way forever.

Someone else who has noticed the parallels is Labour activist James Doran, who has spent years blogging about the “Pasokification” of his party. The picture he paints is of constituency party meetings devoid of political activism or engagement, where the bulk of the members feel betrayed by their leadership and the couple of attendees under 40 are either Blairite careerists or far-left agitators. Again, compare this to Syriza or Spain’s Podemos, both movements where all the answers are not handed down on tablets of stone.

The big difference here is obviously that Britain has the system of ballot-box protectionism otherwise known as first past the post, which makes the two main parties the repository for most wannabe politicians. It is unlikely that the SNP would ever have gained the potency it has today without the incubator of the Holyrood parliament and its system of PR. But to look at the Scottish referendum, the rise of the Greens and even Ukip is to see how Labour and the Conservatives have long stopped being the centre of political excitement.

Just like Pasok, Labour has spent decades under the influence of Tina: the idea that “there is no alternative”, either in how to run an economy or how to run a social democratic party. The rise of Syriza shows how that rule can be broken. And for all its labelling as a far-left party, much of Syriza’s platform is simply leftwing social democracy spoken as the politicians believe in it, rather than as just another dead slogan to mouth.

Over the past few years, Syriza’s thinkers have sometimes quoted a text as a kind of description of their window of opportunity. It is from Antonio Gramsci’s Prison Notebooks. In it, the Italian communist notes: “At a certain point in their historical lives, social classes become detached from their traditional parties … The particular men who constitute, represent, and lead them, are no longer recognised by their class (or fraction of a class) as its expression.”

That applies to Greece, yes. But tell me it is not also true of Britain.