So, it happened.

In a national referendum, on a turnout of more than 72 percent, 52 percent of British voters decided that they wanted their nation to exit — hence, Brexit — the European Union. The process will take a while, but Britain is on its way out the door.

I watched the referendum unfold in London, where almost no one believed Brexit would win.

But in the end, the English north, with its working-class voters, cast ballots heavily for Brexit, heavily enough to outweigh the votes of London and Scotland, which wanted to remain in the EU. Indeed, apart from London itself, all of England’s regions, and Wales, wanted out.

The pollsters certainly didn’t get it right. Perhaps they sampled the wrong people — too many prosperous voters who like the EU, too few workers who don’t. They made a similar mistake in 2015, when they missed the result of the last British election.

As I wrote in my last column, one of the big issues in the referendum was immigration. But it’s too simple to say it was immigration that won it for Brexit.

advertisement | advertise on newsday

Basically, the reason the EU was unpopular on Thursday was that it was unpopular last year, and the year before that, and a decade ago, and even two decades ago. The EU’s unpopularity has certainly waxed and waned, but, by and large, it’s waxed.

This isn’t the first referendum Britain’s held on Europe. In 1975, the pro-Europe side won by a 2-to-1 margin. This time, it lost. Immigration certainly mattered to that result.

But what told in the end was that the British people now have 41 more years of experience with the EU than they had the last time they voted. The EU’s harshest enemy was time.

Familiarity doesn’t always breed contempt — as Churchill joked, without a degree of familiarity, you can’t breed anything at all. But the longer people hang around the EU, the more unpopular it tends to become. Immigration was just one of the things that, over the years, bled the EU.

Brexit didn’t win because of a sudden revolt, as we’ve seen this year in the United States. It won because of decades of effort on the part of Euroskeptics, and decades of British disappointment with the EU. Those Euroskeptic efforts won the argument.

And last week, they won the vote as a result.

Ted R. Bromund is a senior research fellow in The Heritage Foundation’s Thatcher Center for Freedom.