As European leaders meet this week to find a way forward from the UK's decision to leave the EU, James Naughtie surveys the mood in France.
A man said to me in Paris, "It's historic." "Yes," I said, but he was talking about the football.
I was thinking about Henry the Fifth, because there is nothing like disappearing into the past to make you think about the present.
You might not have thought, a few days ago, that the fourth volume of Jonathan Sumption's magisterial and intoxicating account of the Hundred Years War would feel like the right book this week. But when the world turns upside down, anything goes.
With European leaders rushing to Brussels like weary delegates to some post-war peace conference, it seems natural to turn to chaotic times to feel at home.
That particular King Henry died at the Château de Vincennes in Paris, just about 600 years ago, when he was only 36.
He had beaten the French at Agincourt and manoeuvred himself to within an inch of the throne, under the empty gaze of a witless king stripped of any real authority in a country where dukes of Burgundy and Gascony and Armagnac (and, you might like to think, Beaujolais and Chablis, too) had laid the ground for the English with their own frantic struggles for power.
Henry died of dysentery not long before he would have become King of France as well as England, a warrior brought down by the dismal workings of mortality when everything was in his grasp.
Two kingdoms. Power. The chance to shape a world of his own.
The beating heart of Europe
And what would have happened?
Well, Paris would surely have been the beating heart of Henry's Europe.
His England, the sceptr'd isle of his grandfather John of Gaunt, would have had to look to this city, with its poise, its culture, its music, its thundering grandeur, even then, and away from itself, like a moon doomed to circle a bigger planet for the rest of time.
The history afterwards would not have been the one we know.
But a victor king died and a weak one survived.
France went its own way, and so did England.
Chance. The throw of the dice. The fate of countries that turns on the instant.
Fearsome mortality, a battle. Or a vote.
No one here these last few days, any more than at home, knows where we are heading.
I did try to raise the Hundred Years War with someone last night, and did not get very far. It didn't seem the moment for the St Crispin's Day speech.
Nor for a discussion of the respective problems of Jean-Claude Junker and David Cameron, and the nightmares that will haunt them down the years.
Someone pointed to Marine Le Pen smiling on the television, which she has been doing a lot. For the same reason, I spoke about football instead.
Better to let it be.
But kings and barons, the different ways of English courts and the ducal rivalries of France, remind you how much does not change.
And, maybe, how these countries, long ago, made themselves different. Not by fate, but chance.
I am heading to the battlefields of The Somme today.
That centenary on Friday touches quite another part of our shared past and the two-minute silence just before 0730 BST will mark the moment when the troops advanced at the start of the most bloody, costly morning in the history of the British army.
But, in Picardy, I might have time to read some more history.
Funnily enough, there is something about the 15th century that is rather appealing just now.