They have perhaps the longest international rivalry in the history of the nation state, a mutual disdain rooted in generations of medieval war, decades of imperialistic antagonism and a cultural dissonance that persists to this day.
A frisson of "fraternité," "entente amicale," and "amitié was rippling through Britain's political class (not to mention the usually francophobe tabloid press) Thursday after one of the most remarkable state visits by a French leader since World War II.
Nicolas Sarkozy, ridiculed at home for his vulgar ways and "bling-bling" taste in accessories (and women), stunned British parliamentarians with a speech of exquisite praise for all things English and a call for a new 21st-century brotherhood between the old adversaries.
There was an extraordinary declaration of thanks for the Churchillian resolve that helped rescue France "when it was virtually wiped out, down on its knees," an expression of gratitude that it is hard to imagine his predecessors ever giving.
There were concrete proposals – for Britain to join France at the heart of Europe, working together to solve some of the big global issues of the day such as climate change, energy, immigration, security, and Afghanistan.
And there was a grand overture: "that together we write a new page in our shared history, that of a new Franco-British brotherhood – a brotherhood for the 21st century."
Members of Parliament didn't know whether to laugh or cry. Formal state visits, steeped in pomp and ceremony and regal protocol, are usually substance-lite. Denis MacShane, a Labour MP, notable francophile, and biographer of former President François Mitterand, said it was the most interesting state visit in many years.
"What was interesting was the tone of his words, the way he spoke, the warmth," Mr. MacShane says. "He was remarkably complimentary about Britain. He knows how to stroke the Brits the right way."
"Sarkozy wants to close the chapter of Gaullism," MacShane adds. "Mitterand and [former French President Jacques] Chirac always kept the British at a distance."
Newspapers returned Mr. Sarkozy's compliments with interest. Tabloids swooned at his supermodel wife, Carla Bruni Sarkozy, who cut a classy, demure figure at a royal banquet on Wednesday night, inviting comparison, albeit perhaps hyperbolic, to Jackie Kennedy and Princess Diana.
In short, it was all a far cry from the usual petulance that has characterized Franco-British relations for a lifetime. Yes, it's been a long time since the two squared off across a battlefield (you have to go back to 1815 for that). But diplomatic hostilities have broken out with unedifying regularity since World War II.
There was Charles de Gaulle's bid to prevent Britain entering the European Union in 1967. There were long-running feuds over a French ban on British beef, France's refugee center located right by the Channel Tunnel, and Britain's EU financial contributions.
So when France dug in its heels over the Iraq war, it was a cue for British tabloids to rush out all the old jokes, including the one about the number of gears on French tanks (five reverse and one forward, in case of attack from behind).
The relationship has not been helped by some particularly explosive personal chemistry. Former British Prime Minister Margaret Thatcher and Mr. Mitterand famously did not get on, he once describing her as "an impossible woman." Tony Blair and Mr. Chirac were not much better. The French leader once reportedly told Mr. Blair he had been "very badly brought up" after he challenged him on a policy point. Chirac was later overheard joking that "we can't trust people who have such bad food."
Yet within that last remark lies a delicate hint of the origins of rapprochement. Britain can no longer be dismissed as a nation of "bad food." Hundreds of French chefs have seen to that. French citizens have moved in the thousands to Britain in recent years, such that London is now, as Sarkozy remarked, the seventh-biggest French city. French accents are ubiquitous: at the school gates, in restaurants, on trains, in clubs and bars.
In return, hundreds of thousands of Brits have moved in the opposite direction and are so numerous in parts of rural France that they are running for office. Cultural barriers, once steep, are being eroded.
A neat example: Thursday's summit was at the Emirates Stadium, home to Arsenal Football Club, which for several years has boasted as many French internationals on its books as English. And it has a French manager, Arsène Wenger. Few fans are complaining, even if it does relegate British players to lower leagues.
Timothy Garton Ash, a British historian and professor of European studies at Oxford University, says old enmities have become "irrelevant" in a world where "we are both medium-sized European powers, where Britain is increasingly a European country, and France is increasingly globalized, and we are all mixed up together indifferent ways including commercially."
But he cautions that Sarkozy's grand overture may not result in a glorious era of Anglo-French bonhomie. At the heart of his appeal was a call for Britain to become more closely engaged with the EU. Britain may be a more European country these days, but political discourse is still dominated by Euroskeptics unconvinced by the case for closer affinity with the 27-nation bloc.
"The political class in France and Germany assumes that the other is their first partner in Europe," he says. "The political class in Westminster certainly doesn't assume that. It assumes that its first partner is the US, and still has quite a lot of reservations about Europe."
Brits would, he adds, be misguided if they thought Sarkozy's offer was about replacing France's long-term partner Germany with a new paramour. "It would be very foolish to understand that it's us instead of Germany," he says, "it's us as well as Germany. A ménage à trois."