UK-shaped hole in EU's Bratislava agenda
Just to be clear, the UK's imminent departure from the European Union was not on the agenda here in Bratislava this week.
Indeed so emphatically, unequivocally, absolutely was it not on the agenda that it was quite difficult to think of anything else.
The full artillery of zoological comparison was deployed to meet the occasion - there were elephants and gorillas in the room, but no British political leaders.
For the first time since the age of the Cod War and the three-day week and bell-bottomed trousers, Europe's political elite had to manage without the input of the UK.
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Officially it was not a summit, but an informal gathering - which is to say the same army of advisers, diplomats, translators and politicians got together as usual, but presumably set about their work in a slightly more devil-may-care fashion.
Make no mistake, though. Bratislava was really about giving Europe a glimpse of a post-Brexit future. This is what the European gatherings of the future are going to look like.
As they arrived and gave their doorstep interviews the leaders spelled out between them what amounts to a daunting to-do list: jobs, growth, prosperity, migration, security, terrorism and border control.
French President Francois Hollande spoke rather grandly of the need to find a new impulse for the European project. More pragmatically, German Chancellor Angela Merkel warned that Europe's problems would not be solved in a single meeting.
Was the UK missed, as the leaders embarked on a Danube river-cruiser for a lunch designed to provide a few appealing television images?
Well, whether you see the British as over-mighty obstructionist foot-draggers or worldly-wise, thrifty pragmatists, there's no doubt that without them things will be different.
A German colleague said rather wistfully that he'd always felt there was a pragmatist "northern coalition" of the Finns, Swedes, Dutch and Germans from which Britain would now be sadly missed.
But others will have to adjust to the UK's departure too.
If you're a passionate federalist for example - someone who thinks the days of the nation state are numbered - then Brexit in theory removes an obstacle to ever-closer union.
And of course before Bratislava you had that British foot-dragging as a useful scapegoat, if your dreams stubbornly refused to come true.
There are plenty of European true-believers who'd like to see much closer defence co-operation for example - perhaps in future even a European army, which wouldn't rely on the United States as Nato does for its guns and its money.
British scepticism - and loyalty to the Atlantic Alliance - has always been portrayed as a brake on progress towards that integrationist goal.
But what if Britain wasn't alone in that scepticism?
What if other European countries were equally dubious about the costs and benefits of European defence co-operation, but had been hiding their own doubts up to now behind Britain's?
If Brexit is to be a kind of hinge of history then Bratislava is not a bad place to listen to its first creakings.
It sits a short distance to the east of Vienna and is one of those central European cities through which the Danube slides serenely towards the sea.
It's also one of those luckless places through which history has surged rather more forcefully.
The architecture helps to tell the story - castles and cathedrals with a touch of the Brothers Grimm about them and apartment blocks in porridge-coloured concrete with the unmistakeable flavour of Soviet domination.
There is a handy ready-reckoner in Eastern Europe for how roughly history has handled your home town: how many different names it has had in different languages.
Bratislava has also been known as Pressbourg, Poszony, Preshporok and Brezalauspurc for example - and was nearly re-christened Wilsonstadt as a tribute to the American president after World War One.
That's not unusual in this part of Europe. A nearby city in western Ukraine has been known in my working lifetime as Lviv, Lvov, and Lwow, and before that was both Lemburg and Leoville - and that's just in relatively recent history.
So the past looks and feels different from the vantage point of Central Europe. And where the European Union may have been seen in the UK as a source of unwanted regulation and instruction, countries which have emerged from Soviet occupation in our lifetimes see in it the promise of prosperity and stability.
The Slovakians put Bratislava Castle at the disposal of the EU leaders who gathered here - and many of them will remember that, when the forces of the Warsaw Pact crushed the brave democratic flowering of the Prague Spring in 1968, the Union that came calling at the castle gates was the Soviet Union, not the European one.
So Brexit will no doubt have been on the minds of the European faithful who gathered here - but so will the thought that many in the eastern half of the Union remember times that were much darker and much more dangerous.