The alacrity European leaders showed in congratulating Emmanuel Macron on his emphatic victory said it all. France’s president-in-waiting is an assiduous advocate of openness and internationalism. He is a committed pro-European, who marched on stage on Sunday night to the strains of the EU’s anthem and pledged in his first address to defend the continent’s values and rebuild its links with citizens. Above all, he is not Marine Le Pen.

Yet the widespread relief at his election — with a commanding 66 per cent of the vote, more than polls had predicted — must be tempered by realism.

Mr Macron’s achievement, becoming the youngest ever occupant of the Elysée Palace with no experience of elected office and none of the supporting machinery of a traditional political party, is astonishing. He was aided by the implosion of his Republican and Socialist rivals and also, thankfully, by the large majority that remains resolved to deny the far-right power, even if they dislike the alternative.

Mr Macron has shown that it is possible to craft a liberal, centrist response to the populist politics of national identity and protectionism. He has done so, not by adopting any diluted version of the National Front’s ideas, but by appealing to voters’ intelligence. He has steadfastly refused either to accept his opponent’s depiction of a nation doomed to decline or to vie with her in promising the unattainable.

It is reassuring to see there is still an audience for this kind of rational argument — and that voters do not seem to have been swayed by security scares, or by the dubious attempts to discredit Mr Macron online in the campaign’s closing stages. Mainstream politicians had prevailed in the Dutch and Austrian elections and the French vote gives Europe grounds to hope that the populist insurgency has peaked.

The president-elect’s battles are only just beginning, of course. He was the first to acknowledge this, warning his supporters of the “immense” task ahead of them.

It is a depressing sign of the times that an election in which more than a third of voters backed the leader of an overtly xenophobic party rooted in anti-Semitism should seem cause for celebration. Ms Le Pen won almost twice as many votes as her father did 15 years ago. She is now styling herself as the official opposition. A quarter of the electorate stayed at home and large numbers opted to spoil their ballot. Mr Macron has a huge job ahead of him to restore faith in the possibility of a vital, democratic, prosperous France.

His promise is to use his five years in office to ensure that none of those who felt driven to vote for the extremes will have cause to do so again. That will require reforms — of the economy, labour market and public sector — of the kind that successive presidents have attempted and failed to sustain.

One advantage of Mr Macron’s repudiation of party politics is that he is not hobbled by promises made to this faction or that during the campaign. He has been forthright and unapologetic about his overall intentions. But to act on them, he will need to legislate. He may have enough momentum for his fledgling En Marche! movement to become the National Assembly’s largest party in next month’s legislative elections but, with the traditional parties regrouping, it is hard to see how he can win an outright majority.

“I will not let any obstacle stop me,” Mr Macron declared on Sunday night. Let us hope he can pull it off. If he succeeds, he might jolt France out of its deep-seated malaise and restore it as a force for reform and renewal across Europe. If he fails, Ms Le Pen will be back next time.