As a Brussels correspondent in the 1990s, Toby Helm reported on the EU at its zenith. Now, as Observer political editor, he returns to a city of uncertainty – over the Greek debt crisis, the future of the euro and the whole political project

Norbert Schwaiger is a true veteran of EU summits. Now in his early 70s, the amiable German recalls with relish the triumphs and disasters from 34 years of service in Brussels as if they all happened yesterday. He chats about Delors, Kohl, Mitterrand, Chirac, Thatcher and the great rows with the British over money. The epic moments of European construction, from the Single European Act in 1986 to the Maastricht treaty in 1992 and the birth of the euro in 1999, are all fresh in his mind.

To catch up with Europe's progress, Schwaiger, a former press officer who retired in 2003, returned to a Brussels summit last week to take the temperature. Much had changed. "The historical idea has faded," he said wistfully. "When we started it was about Germany and France and the Benelux countries building a new Europe to stop the endless wars. Germany, and that generation of Germans, was ashamed of Hitler. It was about creating security, a secure Europe and a secure economy. Then they wanted to have Europe as their new home country."

As EU officials from 27 countries milled around the giant Justus Lipsius building, the venue of a summit dominated by the dire economic plight of Greece and the resulting existential threat to the euro and the EU itself, the contrast in mood could not have been starker from the heyday of integration that Schwaiger had known.

The talk was no longer of high ideals and "more Europe", but of mere survival for the European project. Where they used to talk of "ever closer union" in the commission press conferences, the phrase i s now rarely, if ever, heard except when referring to history. José Manuel Barroso, the pragmatic European commission president, set his sights at this summit on "stability" for the foreseeable future, meaning the EU will do well to steady the ship in the face of Greece's financial implosion and possible exit from the single currency. Never mind any new European dreams.

From Schwaiger's perspective, one of the reasons why Europe has run out of idealism is the passage of time. He argues that Germany's postwar guilt, which did so much to power the European project, no longer drives young Germans to think about the EU as their parents and grandparents did. "In Germany the new generation, just out of school, has no memory of this," he says. Instead the young see a Germany united from its former east and west, communism fallen and a continent no longer haunted by its past or racked by the fear that it could plunge back into war. Much of Europe's original raison d'être has disappeared and Germany is now less willing to be its unquestioning, selfless paymaster.

Greece's plight has greatly sharpened the sense, evident for several years now, that Europe has lost its drive and, in some quarters, is losing its self-belief.

But some things in the European Union, particularly in Brussels, never change, and therein, perhaps, lie the roots of its problem. Outside the unreal echo chamber that is the Justus Lipsius, the building work for the EU empire of which the founding fathers dreamed continues apace. Vast new glass edifices are being erected in the perpetual chaos of dust and noise that is part of life in the EU's capital.

The physical construction of a united Europe seems to carry on in ignorance of the crises unfolding in the wider world. Up the road from the Justus Lipsius they are preparing the home for a new European diplomatic service, where many hundreds of mandarins will be based. Herman Van Rompuy, the first permanent president of the European council, briefed heads of government last Thursday night over dinner about the spanking new £280m base in which he will entertain EU leaders from 2014. David Cameron was apparently incensed and briefed the British press the next morning that European leaders did not "get it" as they showed off their "gilded cages" while Europe's citizens endured austerity and Greece was on the rocks.

Van Rompuy's talk of his new "palace" offered a perfect excuse for Cameron to court popularity at home by attacking a Europe with its head still stuck in the clouds. But whether or not it was political opportunism, the prime minister had a point. Barroso may show refreshing realism, but too many of those at the centre of the EU project still remain in semi-denial. The new pragmatists seem at odds with an old order that refuses to give up. "We do have to respond differently and too often we fail to do so. We all have to rid ourselves of this idea that we are just programmed to march ever onwards," said one EU official.

Early in 1999, shortly after the launch of the euro, Romano Prodi, then president-elect of the commission, was not content with realising Europe's most ambitious venture thus far, the merging of 11 national currencies into one. Instead he put his foot harder down on the integration pedal. "The single market was the theme of the 80s," he declared. "The 90s was the decade of the single European currency. We must now face the difficult task of moving towards a single economy, a single political unity."

Europe worked in those days on the assumption that if it ever stood still it would fail. As a result, it went at breakneck speed and bent its own rules along the way. In the planning of the euro the desire to create a massively ambitious currency union across much of the EU was achieved only by ignoring its own economic rulebook.

In the run-up to the euro's launch, painful battles were fought between France and Germany to establish a stability pact to ensure members of the currency zone observed fiscal discipline. Euro countries, it was agreed, would have to have debt-to-GDP ratios of no more than 60% and deficit-to-GDP ratios of no more than 3%. "It was about Germany getting a stable euro, a euro like the deutschmark," observed a German official. But when the original 11 countries were admitted in 1999, no fewer than six were allowed in with debt levels well over the required level. The rules were waived as long as their debts and deficits were moving in the right direction.

In the case of Belgium and Italy, their debt was nearer 100% of GDP than 60% – but in they went. The same leniency was shown when Greece joined in 2001, with a debt ratio heading towards double the level required. "We might have been a little too relaxed with Greece," said Richard Corbett, a former Labour MEP who now works as an adviser for Van Rompuy. Within a few years, France and Germany were also busting the stability pact rules.

Twelve years on from the birth of the euro, as the EU prepares to lend more billions to Greece after an initial €110bn failed to do the trick, serious figures in the European debate now believe the euro's crisis could cause the entire EU project to implode. Sir Stephen Wall, Britain's ambassador to Brussels under John Major and Tony Blair – and no kneejerk Eurosceptic – declared recently that the EU was "on the way out". He added: "After all, very few institutions last for ever." A decade ago he could never have predicted he would say such a thing.

On Wednesday, the Greek parliament will vote on a new package of austerity cuts and sweeping economic reforms. If the vote is in favour, the EU will press ahead with its next bailout. No one is sure, however, whether pumping in more EU money will be enough to prevent Athens from defaulting on its massive debts. The fear is that it will not be, and that a Greek default will cause Portugal, Ireland and even Spain to do the same. The effects of that would be appalling, destroying the credit of banks across Europe and further afield that are exposed to Greek debt, wrecking their ability to lend, and landing the default insurance market across the globe with untold costs. The nightmare scenario is another economic crisis on the scale of 2008.

But still the idea – increasingly entertained by economists – that it could all end with Greece being forced out of the euro is not one anyone in Brussels will readily accept. "Greece leaving would just make matters worse, as the Greek currency would devalue, while its debt would remain in euros," said Corbett. "And people would take fright and move their money out of the country."

Kostas Karkagiannis, the Brussels correspondent of the Greek newspaper Kathimerini, says the Greeks will fight to stay in the euro and the EU because it is their best hope. Greeks, he says, see the EU as a haven. "All these European laws are so much better than ours. At least with the EU laws you have a chance of them being implemented. What will happen if we leave the euro with all our debt in euros? Think about the devaluation, think about the inflation. We will go back 25 or 30 years."

That may be the view in Greece, but the prospect of throwing so much money to the stricken country is not one that appeals to other states in an EU of supposedly equal partners. Tensions are deepening between the union's wealthier northern nations and poorer south.

The immediate challenge for Brussels is to ease the Greek crisis and hope that its economy can be revived. The aim is to get private banks that are exposed to Greek debt to exchange them for new loans. Then pray the rescue measures work. In the meantime, plans are being pushed through the European parliament to toughen up the kind of rules that were supposed to apply under the stability pact. There will be new surveillance "early warning" measures aimed at ensuring eurozone countries are not heading into economic trouble, such as unsustainable property booms.

Optimists in the EU try to convince themselves that something good could come from the crisis – meaning more economic integration and harmonisation of taxes – steps towards the single EU economy of which Prodi dreamed. One of the arguments the commission deploys to calm anxiety is to make out that Europe is no stranger to crises – indeed, it says, it has always thrived on them.

Mark Gray, a spokesman for Barroso, said: "The temptation is to look back at the past through rose-tinted spectacles. But there were always peaks and troughs." He points to the queue of countries wanting to join the EU and the euro as evidence that they are more relevant than ever in a globalised world. Corbett believes that Europe could even emerge stronger. "That is what we hope will happen," he says. "But you don't hear much about that in the British press."