Much was made yesterday of Radio 4s enchanting scoop: a document showing that in 1956 the French Prime Minister, Guy Mollet, asked Anthony Eden for formal union between the UK and France. When Eden blushingly turned him down (“Why, M Mollet! this is so sudden!”) the importunate Frenchman offered to join the Commonwealth and thought “there need be no difficulty over France accepting the headship of Her Majesty”. On being told this by the BBC reporter, a professor of history at the Sorbonne went into an outbreak of stuttering hysteria — “Preposterous! . . .” It didn’t happen. A year later France chummed up with Germany instead for the long march to the present-day EU.

I daresay that on waking to this news, most of us checked the calendar to see if April had arrived. Only P-Y Gerbeau, that Anglophile enthusiast, pointed at Churchill’s 1940 proposal for “A solemn Act of Union” between France and Britain with joint defence, foreign, financial and economic policies. But those were the grim days of the Fall of France. The revival of the idea in 1956 — when Nancy Mitford’s English-rose heroines and improbably irresistible Frenchmen were basking in la différence and Britain had happily returned to boiled cabbage and Ealing comedies — is a bit of a stunner. It gives rise to fascinating daydreams.

Could it have lasted, a United Kingdom stretching from Shetland to the Mediterranean? How would we have influenced one another, culturally and psychologically? What about language? Religion? Education? America? What sort of governments would a half-French electorate have helped us to choose? Would the British Left have been strengthened? Would we have taught them binge drinking, or would they have taught our young to sip? Would Englishwomen be thinner, Frenchwomen fatter?

Would we have high taxes and superb maternity care, or would there be a gigantic flabby NHS, bankrupting hospitals from Stromness to St-Jean-de-Luz? Would the suppository really have caught on in Birmingham? Would there by now be a militant French Separatist movement, or indeed a British one, and how would this affect the smaller separatisms of Scotland and the Basques? Would government have been less inclined to post-imperial guilt and anxious multiculturalism, and more like the brutally pragmatic French, who ban hijabs and interrogate terrorist suspects without a lawyer? Would our cities still have evolved with sink estates next to affluent streets, or would we have adopted the French way of confining the alienated poor in grim satellite suburbs?

Large questions and small ones cluster in, all equally beguiling. The entanglement of our history from the Norman Conquest to the Flanders war graves makes our differences piquant. Fashionable Parisians dress their dogs in le Burberry coats, English dreamers long for Provence.

My own sense of difference began more than 40 years ago when, for three years, I was pitched into a French school. After a few weeks of language lessons with an elderly nun I became a French schoolgirl. Aged 10, we were issued a litre of beer between eight of us at lunch; I experienced white gloves, pinafores, curtseying and bourgeois children’s tea-parties with third-person invitations and creamed mushroom sandwiches. A 1960s playdate was part of social training: when I owned a Petit Biologiste set and a craze for natural history, a stiff invitation arrived saying “Véronique invite Elisabeth pour le gouter, et pour disséquer un ver de terre”.

Years later, reading Charlotte Brontë’s Villette about a 19th-century school in France, I immediately recognised the culture of “surveillance” in France and the contrast with the English dependence on internalised self-discipline and being “put on one’s honour”. To this day I note the after-effects of “surveillance” whenever I see how French schoolchildren behave in museums when their minders aren’t looking.

There are better things to notice too, and not just the food and the flourish and the curly string in patisseries. France has a fierce respect for brainy argument and a scorn for empty small-talk. Interviewing French politicians is unnerving: with all the intellectual arrogance of the Grandes Écoles they throw your questions back at you rather than droning out prepared statements with a panicky grin. And yet, decade for decade, it is hard to claim that France has been any better governed than Britain.

But it talks better and thinks harder: When my French publisher discovered that I could just about cope with speaking in French, I got summoned to broadcast debates, on one occasion the terrifying TV discussion show Bouillon de Culture. There was a worker priest, a French soap star, a psychiatrist and me. I realised within minutes that the sweet, soppy British way of doing these things — everyone having their turn to speak, civil attempts at consensus, no “elitist” intellectualism to frighten the listener, nobody being rude to beautiful actresses — is footling baby-talk in comparison.

To be brutal, the host Bernard Pivot made Melvyn Bragg look like a smiling Teletubby. The next morning I was on a local reggae station with a scruffball host and expected a softer ride; I did not get it. Where an English DJ would have warmed up with inconsequential personal chat, this one dived straight into my “concept” and started arguing. It was as stimulating as a cold shower. It happens every time I am lured, against better judgment, into public argument in French.

How different would our union have made us both? Would we have coped as compatriots? Even for a week? On this occasion, at least, I suspect Eden knew what he was doing. Phew.

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