For five years – since 2010 – it has seemed to be a matter of when, not whether, Greece defaults on its debts and leaves the euro.

Alexis Tsipras
Juncker has warned Tsipras the 'friendship' of other nations towards Greece could become strainedReuters

But it has never happened, thanks to the apparently bottomless pockets of the Germans, to the traditional flexibility of the European Central Bank in interpreting the rules (a flexibility from which, in the early days of the single currency, both France and Germany benefited) and to the fear among members of the European Commission not that an exit from the euro would undermine the European economy (though it would), but that it might undermine the whole European project.

The process of ever-closer union has always been considered irreversible. A country getting out of the currency that was supposed to symbolise the unity of Europe, and doing so by asserting the principles of sovereignty that are anathematic to the EU mind, would be a reverse and a half, to put it mildly.

Over the weekend the G7 summit, meeting in Bavaria, spent much time discussing the parlous state of Greece's relations with its EU partners. On Friday (5 June) Greece had declined to make a payment of €300m (£219m, $334m) to the International Monetary Fund, rolling it over to the end of the month as it was entitled to do.

However, there will be no means to pay it then either. The IMF is so far being reasonable about it, and a default process where it is concerned can take two years or more. The EU, however, is starting to have its patience taxed by Greece's behaviour.

Alexis Tsipras, its radical prime minister, tells his people that he will not force another period of austerity upon them, after what they have endured in the last five years.

He believes that the rest of the EU, notably Germany, the paymaster of the organisation, is so desperate to keep the show on the road that they will tolerate any degree of delinquency by Greece in order to keep the country in the euro. The signs over the weekend were that his bluff might be about to be called.

Jean-Claude Juncker, the president of the European Commission, warned Greece that if it did not comply with the stringent measures the troika – the Commission, the European Central Bank and the IMF – wish to continue to impose upon it, there would be a serious strain placed on the "friendship" other nations felt towards Greece.

National first, European second

That, however, was mild compared with what Martin Schulz, the president of the European Parliament, had to say. He warned the Greeks of "dramatic consequences" if they did not find common ground with their creditors. He reminded Tsipras that he had a responsibility towards the wider EU and not merely towards the people of Greece.

That remark goes to the heart of the problem of sovereignty, and the unreality with which the Syriza government is addressing this financial crisis. It wants to stay in the European Union and, it appears, in the euro itself; but it wants to play by none of the political or economic rules that govern those institutions.

It wants to participate in the euro and the EU on a level that requires the surrender of much of its national sovereignty, yet it wishes to retain important aspects of that sovereignty that contradicts the nature of that participation.

Merkel and Hollande
France and Germany benefited from the flexibility of the ECB in the early days of the single currencyGetty

For good measure, Schulz also seemed to hint that if Greece got out of the euro, it would have to leave the EU: that, though, is probably just an off-the-cuff remark aimed to sow fear and dissent.

This is an entirely unsustainable position. There is anger in countries such as Ireland, where huge sacrifices were made in the years after 2008, that Greece might be getting special treatment and is not being forced to make the sort of sacrifices the Irish made.

Equally, there is little doubt among those in the financial markets that Greece can never pay its debts, and that, for the moment, it refuses to play by the rules of the currency zone of which it is a part.

If that is the approach, then as far as Greece is concerned the euro has to be over: for if the Germans and others allow this to carry on, in the end the only option for Greece would be to make a mockery of a currency system and a shared economic project that they regard as fundamental to the future of the EU.

One problem with the EU – and the British government may soon find this out – is that for all Schulz's preaching the people of the various states consider themselves to be national first and European second. When a German politician tells the Greeks to behave for the common good and not for their own he is met with a mixture of ridicule and contempt.

Tsipras made all sort of promises about ending austerity when he was elected last winter. Now he has either to betray Europe or betray Greece. When he makes the predictable choice, he had just better hope that what follows is not something worse than austerity.

Dr Simon Heffer is a British commentator and author who has written columns for The Daily Mail, The Daily Telegraph, The Spectator and The New Statesman. He is the biographer of Enoch Powell, Thomas Carlyle and Ralph Vaughan Williams and recently published High Minds: The Victorians And The Birth Of Modern Britain.