Maison Bour, the boulangerie, pâtisserie and chocolaterie at 82 avenue des Alpes in Cagnes-sur-Mer, a few kilometres west of Nice, is a marvel of French civilisation.

Every morning, when I went there to get our bread, my spirits were raised by the speed and skill with which its large and industrious staff constantly replenished the immaculate, delicious and astonishingly diverse display of breads, cakes, tarts, chocolate and other delights on which one could feast one’s eyes while waiting for a few minutes to be served, for this was the height of the tourist season, and the establishment is deservedly popular.

Along the coast, in Nice itself, are other marvels of French civilisation, including many fine buildings of the Belle Epoque. What could be more delightful than to climb to the Tour Bellanda and sit in the shade, gazing along the graceful curve of the Promenade des Anglais?

But on the evening of 14 July, a few minutes after the Bastille Day firework display, 86 people were killed when Mohamed Lahouaiej-Bouhlel drove a lorry through the crowds along that very promenade.

Nice is now full of soldiers, patrolling the streets in threes, their firearms at the ready. They look, for the most part, very young and inexperienced: a show of force, but not a reassuring one.

And we have seen photographs of armed police officers telling a woman to remove the burkini she was wearing on the beach at Nice. Once again, this is not a reassuring spectacle, for it suggests a desperate lack of confidence on the part of the French authorities; a desperate desire to be seen doing something, whether or not the action is of the slightest value, or is counter-productive.

What has gone wrong in France? The best recent answer I have seen to that question was offered by Ambrose Evans-Pritchard, in yesterday’s Daily Telegraph. He wrote:

“A democracy can endure deflation policies for only so long. The attrition has wasted the French centre-right and the centre-left by turns, and now threatens the Fifth Republic itself.

The maturing crisis has echoes of 1936, when the French people tired of ‘deflation decrees’ and turned to the once unthinkable Front Populaire, smashing what remained of the Gold Standard.

Former Gaulliste president Nicolas Sarkozy has caught the headlines this week, launching a come-back bid with a package of hard-Right policies unseen in a western European democracy in modern times.

But the uproar on the Left is just as revealing. Arnaud Montebourg, the enfant terrible of the Socialist movement, has launched his own bid for the Socialist Party with a critique of such ferocity that it bears examination.

The former economy minister says France voted for a left-wing French manifesto four years ago and ended up with a ‘right-wing German policy regime’. This is objectively true. The vote was meaningless.”

France has been unable, as a member of the euro, to follow the policies it needs. The French national interest has been misinterpreted to mean following the policies that Germany and the European Central Bank require.

When those policies turned out to be wrong for France, nothing could be done to alter course. This is a disaster which plays into the hands of the Front National, of which the French political class is now terrified.

So in order to suggest it is still somehow in charge, it sends raw recruits onto the streets, and dictates what bathing costumes can be worn by Muslim women. Nationalistic gestures are meant to fill the gap left by the lost of national sovereignty, but instead look like an admission of impotence.

Not only are France’s Muslims unintegrated: it is harder and harder to discern the nation into which they could be integrated.

The founders of the European Union saw it as the answer to the national rivalries which had led to terrible wars. For the French political class, it seemed to offer release from fear of Germany. For the German political class, it seemed to offer release from the shame of being German.

The EU was a kind of liberation. The old world of national rivalries would wither away, and be replaced by a Europe in which such competition had become unthinkable, because wider loyalties now prevailed. Perverted nationalism would be replaced by a benevolent supranationalism.

The Germans were so swayed by this thinking that they agreed to get rid of their national currency, the German mark. The French and many others were so swayed by this thinking that they supposed the replacement of their own currencies with the euro would liberate them from German economic domination, and raise them to German levels of prosperity.

What a blunder. The abolition of exchange rates removed the ability of economies with quite different levels of productivity to make the adjustments needed to reflect those differences. The effect of pretending all these economies are the same is to show how different they are.

The members of the single currency find themselves placed on Procrustes’ bed. The agony is excruciating, but still the politicians pretend it can somehow be made to work.

In France and elsewhere, perverted nationalists now see themselves with great opportunities. For the only true answer to perverted nationalism is healthy nationalism, and when the European Central Bank is running the show, healthy nationalism has ceased to be possible.

In the United Kingdom, we now have the chance to show we are capable of the healthy nationalism, and healthy co-operation with sovereign neighbours, which are required. If we can manage this, the case for a Europe of nation states will become unanswerable.