It says a lot about the many contradictions and new dynamics unfolding in Europe today that the British prime minister, representing the historically most solid democracy within the EU, has found himself in recent weeks having to court the leaders of two member states, Poland and Hungary, responsible for much backsliding on democratic norms.

It is one of the sad ironies attached to David Cameron’s referendum plan that what should have been a strong British voice on upholding common values in Europe is now hardly even a squeak. If there ever was a sign of British influence on the wane, this is it.

Nor is it reassuring that, amid the domestic squabbling of the “Brexit” debate, the wider European strategic picture has all but dropped out of sight. Yet there are things going on that Britain would do well to pay closer attention to. As if Europe didn’t have enough problems, a new faultline has appeared: Poland is now under EU commission supervision, through a “rule of law mechanism” activated this week in Brussels for the first time.

The largest central European country, long a poster child of post-communist transition, and which has had an important say in European policies towards the east and Russia, has in effect been blacklisted. Reasons for this lie in the policies of its new nationalist, conservative and Eurosceptic Law and Justice government, elected last October. There has been a worrying rush to discipline the media, the judiciary and parts of the civil service – in effect, trampling over key checks and balances.

That EU institutions have put Poland’s new leaders under special measures is a good thing. After all, European democratic norms only exist if they are protected. But this is a case where geopolitics can hardly be ignored, and where history looms heavily.

German-Polish rapprochement has been a staple of European stability and enlargement over the past 25 years

For Europe, the biggest risk over Poland relates not just to the rule of law but to the damage that could be done to one of Europe’s key pillars: German-Polish post-cold war reconciliation.

Just as Franco-German reconciliation was essential to the European project from its founding in the 1950s, German-Polish rapprochement has been a staple of European stability and enlargement over the past 25 years. That picture has suddenly turned bleak.

Germany is being framed by the new Polish ruling elite as an enemy, with one magazine even depicting Angela Merkel in a Nazi uniform. The contrast could not be starker with the message given five years ago by the then Polish foreign minister Radek Sikorski, who described Germany as “Europe’s indispensable nation” and said he feared “German power less than German inactivity”. No doubt Sikorski had the eurozone crisis in mind at the time, but the historical sweep of his language was obvious.

That the new Polish government wants to conflate Germany with all the woes it sees in the EU is one thing – other critics of Brussels, in Greece and elsewhere, have resorted to similar reflexes in recent years. But this time a strategic divide risks opening up in the heart of Europe.

It is significant that Jarosław Kaczyński, who runs Poland’s majority party, held a long one-to-one meeting with Hungary’s prime minister Viktor Orbán last week, seemingly aimed at consolidating a central European populistic, illiberal axis, intended to counter pressure from Brussels or western European nations. This is one development Britain should pay closer attention to – and not just because Cameron has a wishlist.

United by an authoritarian, nationalistic streak, Poland and Hungary can now work on spreading their political alliance to neighbouring states, where populism is on the rise. The refugee issue is an obvious rallying point. On this issue as on others, from climate change to sanctions, the ability of EU states to act together is ultimately at stake.

With Britain more or less out of the picture, and with France more focused on counter-terrorism, it will be yet again up to Merkel to try to address this new problem of European cohesion. On one hand, that is a shame, because for many historical reasons Britain and France have a special relationship with Poland. On the other hand, it is hardly surprising. Poland’s economy is closely connected to Germany’s.

Merkel has stayed remarkably aloof from the dispute, playing for time as she often does. Meanwhile Martin Schulz, the German head of the European parliament – which is due to debate Poland’s democratic backsliding on Tuesday – has lashed out at the Kaczyński team with talk of a “coup” and of a “Putinisation of European politics”. Some EU officials say they wouldn’t be surprised if Merkel suddenly met the new Polish prime minister for a hard-headed conversation, just as she did with Orbán last year when the Ukrainian crisis required European unity.

Of course, it doesn’t help that the EU has mostly let Orbán off the hook over his autocratic methods. Coming down hard now on Poland, however justified it may be, could be taken as a double standard. Stepping back, all this shows the extent to which Europe’s reunification after 1989 remains a work in progress, even if the process has brought so many accomplishments and has inspired so many, in Ukraine and beyond. There is no risk of Poland dropping out of the EU – unlike Britain – but, taken together, the faultlines are dangerous. British politicians would be mistaken to think the German-Polish split is somebody else’s business, far away.