It’s funny how quickly things go from being inevitable to being unthinkable. Take the euro. Abolishing the pound has never been popular in Britain. But, when the single currency was launched, three out of four people thought that Britain would end up joining it, even though they personally were against the idea. Pro-euro campaigners used to quote this statistic triumphantly. Once voters had accepted that membership was inevitable, they believed, it would be only a matter of time before they came to support it.

How different things look today. Almost no one now thinks that Britain will abandon sterling. The Bank of England has just invited people to submit designs for a new generation of coins, intended to last for the next 20 years. Even the former Chancellor of the Exchequer, Kenneth Clarke, probably the most Europhile politician in the English-speaking world, said last week that the euro had been a mistake.

Suddenly, the question is not who will be next to join the euro-zone – Britain, Denmark and Sweden have all comfortably outperformed the participating states – but who will be first to leave it. Italian shopkeepers are beginning to accept lire again, to the delight of their customers. Even in the Netherlands, commentators are beginning to mutter against the new coinage.

Remove the sense of fatalism from the European project and it begins to look surprisingly vulnerable. One of the more brilliant of the Eurocrats’ tactics was to cast their opponents as being on the wrong side of history. The political unification of our continent was presented, not simply as one among many competing ideas, but as Europe’s destiny. It followed that those who opposed it were old-fashioned, narrow-minded, unwilling to embrace the future. Since people don’t like to think of themselves in these terms, they tended to swallow their doubts and go along with the idea.

Not any more. A striking feature of the recent Euro-referendums was the age profile of the voters. In both France and the Netherlands, people under 25 were the most likely to vote “No”, those over 55 the most likely to vote “Yes”. It was the same when Denmark and Sweden voted on the euro, and when Ireland voted on the Nice Treaty. Indeed, although overall support for the EU varies from country to country, one thing is true everywhere: the most pro-European voters are middle-class men in their fifties and sixties.

This is hardly surprising. When they were young, European integration was the coming thing. Built into the structure of the EU are ideas that were all the rage during the post-war period: big trade unions, a powerful role for the state, a controlled economy. Those were the days when people tended to think that big was beautiful, and that regional blocs were the future.

For today’s generation, accustomed to the internet and to cheap air travel, such thinking seems outdated. The central geopolitical fact of their lives is not the Second World War, but the fragmentation of first Comecon and then the USSR itself into more manageable units. Today’s young people have seen tiny statelets outperforming their large neighbours (compare Singapore to Malaysia, Hong Kong to China, Monaco to France, Brunei to Indonesia – or, for that matter, Switzerland to the EU). To them, the idea of a vast pan-continental state looks like what it is: a concept left over from the 1950s.

I don’t believe that the EU will unravel tomorrow. A political system can survive for a long time without public enthusiasm, sustained by apathy, bureaucratic inertia and the self-interest of those who run it. But Europe no longer has the feel of an idea whose time has come. Take that away, and it can only be a matter of time before the institutions themselves begin to fall apart.

This article was first published in the German newspaper Die Welt on 2 September 2005