Britain is no stranger to barriers. Today, almost all of them lie in ruins.

https://www.washingtonpost.com/outlook/visiting-the-roman-walls-in-britain-as-the-nation-debates-new-barriers/2019/09/05/ab7fba8c-cf7d-11e9-9031-519885a08a86_story.html

Britain is no stranger to boundaries. From Roman fortifications to medieval civic defenses, it is crisscrossed by layer upon layer of borders that have been erased, abandoned, forgotten as years and empires have moved on. Visiting these structures — typically worn down to knobbles of stray masonry — it is impossible to view them as anything but sad. On a long enough time scale, every defense becomes permeable, every hold can be breached, so that it becomes difficult to understand what borders the walls were consecrating in the first place. The remains of what were once London’s outer limits are today nestled amid a thicket of urban growth at the metropolis’s center. Not far from where weighty gates once regulated ingress and egress from the city, major motorways whir with the sound of unimpeded traffic at all hours while, below, the world’s oldest subway system snakes its way, ferrying millions of passengers each day. It is not the people crossing these bygone boundaries who are intruders; rather, it is the walls themselves that have become the intruders.

To visit ancient walls in today’s Britain — to observe their discontinuity and in many cases their complete obliteration — is to understand quite forcefully the silliness of these efforts at division. Many have been worn down gradually by the wind and the rain and then finally cut away entirely by excavators’ spades: The stones of Hadrian’s Wall, for instance, would over the centuries find their way into cowsheds, country churches, grain mills and manor houses. Humans have no greater reverence for delimitations that have lost their meaning than do the elements, merely more expedient means of disposing of them. These partially dismantled structures are testaments to the artificiality of national divisions, but also to the perspective that a remove of several centuries grants. At a time when the fires of nationalism are being stoked as a powerful force of separation, we would do well to remember the many boundaries that once seemed natural and absolute to their makers but that have since faded in relevance and crumbled into dust.

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This should remind all of how useless Trump's great border wall will be. And how in the future it will be meaningless.