When historians seek to explain an event, they often divide their explanation into three parts. In the long run—what the French Annales School called the longue durée—there are deep historical structures, mental frameworks or other slow-to-change systems. In the intermediate term, there are background conditions—more susceptible to change and more shaped by politics than the longue durée, but still mostly beyond the ability of a single individual to affect, at least in any rapid way. Then, of course, there are the short-term factors, the immediately precipitating causes, which are often political.

On Brexit, there is a lot to say about all of these. But the background conditions have received the least attention. Brexit is often described as the result of populist anger, as a populist backlash, or even a populist rebellion. Indeed, President Obama spoke of Brexit in precisely those terms late last week. But the more Brexit reflects those background conditions, the less satisfactory this explanation becomes. After all, if British opinion on the EU has not changed dramatically, it is hard to say Britain is in the midst of a sudden burst of populist anger.