For the past couple of years, one of the abiding themes of the Brexit debate has been about its effect on a city beyond the shores of Britain.
We have wondered whether Calais could cope, and the standard answer has tended to be an abrupt "no".
That assumption has come to frame much of the debate. Many people, across British politics and business, have taken it as a read that Brexit would mean more onerous customs checks at Calais, which would mean queues, delays and knock-on effects for the economy.
But what if that was wrong? What if Calais was actually prepared for the Brexit storm? What if the delays didn't happen? How would that change our model? It is a question that we should start to think about.
I have spent the past couple of days in Calais, talking to the people who run the port and the Eurotunnel facility, as well as politicians and hauliers. And far from a picture of gloom and chaos, what comes across is a city that has long since faced up to challenges. While British politicians have dithered, it would appear that Calais has decided to act.
Eurotunnel has spent around £13m doing work to prepare for Brexit. The port has thrown around £5m at the challenge. Both have followed the same principle of trying to pre-empt future problems and build the solutions now. And both think that the problems are the same.
So here they are. At the moment, British lorry drivers come off a ferry, or emerge from the Eurotunnel, and then drive straight out with the bare minimum of checks. In the future, that won't be as straightforward. Once the UK leaves the European Union, more customs checks will - legally - have to happen.
To do these on the ground would certainly cause delays and frustration. So, instead, both places are relying on so-called e-declarations - where goods are recorded and tracked on official websites. A haulier inputs his load on to that system and then waits to be told whether he has been assigned to either the green or orange lane at customs.
If it's green, the driver goes straight out, just like now. If it's orange (and, yes, that is just the old red customs lane repainted in a less intimidating colour) then he or she has to go to a separate area to talk to customs officials.
But, and here's the crucial bit, the process is designed so that the lorries in the orange lane don't slow down anyone else. On paper, the more-than 90% of vehicles that don't have to visit customs will pass through Calais in the same way they do now.
The lorries that are checked will fall into a few main categories. Firstly, people who've got the paperwork wrong. Then a percentage of hauliers who are carrying perishable goods - meat, fish and vegetables, for instance. And thirdly livestock or racehorses.
Even within those categories, not everyone will be checked. I've visited the customs area for the Eurotunnel, which was built to the specification of French customs officials. It's big, but it's not vast. One hundred lorries can park there and about a dozen can be checked simultaneously. They're clearly not anticipating anything more than a small fraction of the trucks coming through.
And all this raises some important questions. For instance, has the threat to "just-in-time" manufacturing in the UK been overstated?
Eurotunnel's John Keefe told me that "it all comes through here because of the speed of the crossing" and that "their challenge is our challenge". He is unshakeable in his opinion that, whenever and however Brexit happens, lorries will face no more delays than they do today.
It is an opinion echoed by the boss of the port of Calais, Jean Marc Puissesseau, who believes the spectre of chaos at Calais has been used by campaigners on either side of the Brexit debate. He, too, is adamant that, as long as the paperwork has been done correctly, lorry drivers will notice little difference.
If these two people are right, then the car, pharmaceutical and retail industries should all breathe a sigh of relief. All will take some convincing, particularly after years of being told to expect chaos, but perhaps there is a seam of untapped optimism in Calais.
And there is another reason to watch what happens with care. The port and the tunnel are both pioneering sophisticated customs systems that, to a great extent, allow for an unobtrusive, invisible border that leans on web-based technology.
Ring a bell? This is exactly the sort of model that has been suggested as the solution to the unsolvable problem of the border between Northern Ireland and the Republic. If it works in Calais, expect to see plenty of people asking if it might be replicated there.
Necessity and fear remain the crucibles of invention and creativity. The companies behind the port and the tunnel in Calais both knew that their business faced a profound threat if they didn't react to the challenge of Brexit.
Both have since done a lot of thinking, planning and spending. In the face of years of dire predictions about how Calais will grind to a halt, the French city could have the final laugh. We now need to wonder whether it's possible that all those warnings were wrong.