In 2002, I moved from London to what was then a blessedly cheaper Paris. London had its almighty banks; Paris was the “Capital of the 19th Century”. In fact, I felt I was emigrating from modernity.

France then had lower average incomes than the UK and got less foreign direct investment (FDI), partly because of its constant strikes. In foreign policy, France acted as a kind of dissident loner whose views were mostly ignored. The countries are twins: two absurdly over-centralised former empires of 67mn people, forever struggling with deindustrialisation, where the past overhangs the present like a shroud. But, back then, the British twin was dominant.

When Rishi Sunak crosses the Channel on March 10 for the first Franco-British leaders’ summit since 2018, he’ll notice the changes. The country whose contours most resemble Britain is starting to replace it. France is taking over some of the UK’s traditional functions.

Almost 20 years ago, I watched on TV as Britain won a momentous if Pyrrhic victory over its neighbour. The UN was debating the coming invasion of Iraq. Dominique de Villepin, France’s foreign minister, spoke against war, in French, while most delegates listened to the translation on their headphones. It was a metaphor for France’s modern role: De Villepin expected to be heard by the world, but wasn’t quite.

He finished, “This message comes to you today from an old country, France . . . ” Jack Straw, Britain’s foreign secretary, replied: “Mr President, I speak on behalf of a very old country, founded in 1066 by the French.” The delegates — almost all listening to him without headphones — guffawed. British wit had pricked French pomposity. The UK, a pillar of what was then called “the international community”, prevailed on Iraq.

France was proved right but didn’t benefit much. In 2008 John Ross, adviser to London’s mayor, sniffed: “We don’t think of ourselves as in competition with Paris. We’ve won that contest.” Nicolas Sarkozy, then the French president, reflected later that the UK “had won the linguistic battle, the financial battle, won the battle of symbols through its monarchy”.

But after 2008, France’s ruling class showed superior survival skills: the financial crisis didn’t enduringly puncture its economy and there was no Frexit. When I asked French industry minister Roland Lescure whether Brexit was benefiting France, he replied: “Yes, without ambiguity. The UK was the haven for FDI in Europe. We are more attractive than ever. I think Britain is less attractive than ever.” With Britain no longer the obvious place for international companies to place their European headquarters, France now tops it for FDI.

You won’t read many headlines about companies relocating existing staff across the Channel. Rather, it’s new investment decisions that favour France. French incomes have equalled British ones — French people work less but make up with higher productivity. Britain now has French-style strikes.

Probably because Paris and London were both imperial capitals, they are western Europe’s only two global metropoles. That makes Paris the potential alternative to London. It’s now eating into London’s big lead in banking and tech, and only partly because of new British weaknesses: the need for visas for European staff, the rules stopping London-based financial firms from servicing European clients, the stagnating City.

Paris is also becoming more appealing to investors. It has more high-speed train routes than London can dream of and is building 196,000 new suburban homes by 2030. The city’s elite can finally handle foreigners in English — as witness Emmanuel Macron and his cadre of practically bilingual ministers.

In diplomatic crises, Washington traditionally phoned London first. But Britain without a seat at the EU table is less useful. It’s afflicted by uncharacteristic political instability, displays an almost Gaullist obsession with going it alone and has recently anointed unserious leaders like Liz Truss and Boris Johnson. Meanwhile, it’s to France’s marginal benefit that the US secretary of state, Antony Blinken, is a francophone Parisian.

Months ago, Macron was still the classic French dissident inside the western alliance, sounding a bit too pro-Putin for everyone else’s liking. Now, as reality forces him back into the alliance, he says he’s backing Ukraine “to victory”. “I think he has changed, for real this time,” Ukraine’s president Volodymyr Zelenskyy recently said. Even Russophile French military officers are turning against the Kremlin as it helps push them out of Africa. Symbolically, France has transferred military tents from Mali to Ukraine’s borders.

I’m going to offend both countries, but France is becoming the new Britain.

Follow Simon on Twitter @KuperSimon and email him at simon.kuper@ft.com

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