Fear builds walls, walls that divide and sort and separate us, one from the other. It also tears down bridges.

With yesterday's vote in Great Britain to abandon the European Union and retreat again behind the English Channel, the voices of fear won. The bridges are coming down, and not just those metaphorical bridges that have linked Britain to the Continent for some 40 years now. Because once walls start going up and bridges start coming down, it's a difficult trend to halt, and it rarely ends well.

Already, in the wake of the Brexit vote, leaders in Scotland and Northern Ireland have renewed efforts to take down bridges of their own, demanding votes that would allow them to separate from England and dismantle Great Britain itself.

And in an irony of history, wallbuilder Donald Trump -- a man who two months ago didn't even know what Brexit is -- was there to witness and endorse it.

“Basically, they took back their country,” he said from Scotland, promoting his Turnberry golf course rather than campaigning for president. “That’s a good thing.”

“A lot has to do with immigration; a lot has to do with the fact that they want to be independent. They are tired of seeing stupid decisions, just like in the U.S. ... There is great similarity between what happens here and my campaign. People want to take their country back.”

He's right, to a degree. In Britain as well as here, fear of immigration has driven the debate. In Britain as well as here, it was older voters who wanted walls built and bridges dismantled in hopes of restoring a lost and mythical past, while younger, less fearful voters overwhelmingly in favor of continued connection, in favor of the future. The elders got their way, committing their children and grandchildren to a world that they themselves will not likely see.

Today the British pound is collapsing, as is the London Stock Exchange, and as interconnected markets do in a globally interconnected economy, markets here and elsewhere are following suit. These may prove to be temporary reactions to uncertainty, especially outside Britain, but in the opinion of most economists the impact on whatever remains of Britain will be long-term and profound.  Credit-rating agencies have already begun to downgrade British debt, and anybody who was contemplating investment in the British economy is undoubtedly pulling back.

In the wake of the historic vote, British Prime Minister David Cameron announced his resignation, effective in October, and other business and political leaders around the world have no doubt been jolted as well. And while they are right to warn about the consequences of this trend and about the demagoguery of those who seek to leverage it, they also need to confront the fact that to a large degree it is the creature of their own hubris.

In the wake of the collapse of communism 30 years ago, capitalism stood unchallenged. It then embarked on an expansion phase in which it has paid little heed to the impact of globalization, income inequality and other problems, insistent that the answer was always a more and more unfettered marketplace. Individuals stripped of jobs, careers, health insurance, community and a brighter future were treated as incidental casualties of the larger project, and we now see the inevitable resentment of that approach. People denied security in one form will seek it in another.

Trump, for his part, sees the situation largely in personal terms, just as he had with the Orlando tragedy. “When the pound goes down, more people are coming to Turnberry, frankly,” he said today. “For traveling and for other things, I think it very well could turn out to be a positive.”

He also posted a Facebook statement:

"A Trump Administration pledges to strengthen our ties with a free and independent Britain, deepening our bonds in commerce, culture and mutual defense. The whole world is more peaceful and stable when our two countries – and our two peoples – are united together, as they will be under a Trump Administration.

Come November, the American people will have the chance to re-declare their independence. Americans will have a chance to vote for trade, immigration and foreign policies that put our citizens first. They will have the chance to reject today’s rule by the global elite, and to embrace real change that delivers a government of, by and for the people. I hope America is watching, it will soon be time to believe in America again."

As the Brexit vote demonstrates, Great Britain is a deeply divided country, but in their rejection of Trump they have found something to united them. Despite his standing as the nominee of one of our two main parties, no prominent British politicians of any party has agreed to meet with him on this trip.  After his purchase of Turnberry, one of the classic golf courses in Britain, British golf officials announced that the course would not host the 2020 British Open, as had been expected.

Because again, once walls start rising and bridges start falling, it's a hard process to stop.