Some of the grand historical barriers mentioned here had what is generally known as 'practical value'.
Trump may be the last person alive that thinks his wall would have it...at least amongst those coming at the issue from a (supposedly) informed position.
All those strange birds that used to whisper in his ear about beautiful walls, travel bans and the like, have since flown the nest.
They surely knew that the wall would primarily be a symbolic act of defiance against the pressures of globalisation. The Donald apparently doesn't.
Britain's watery Brexit 'wall' features much of the same awkward disconnect between practical and symbolic value.
And its construction remains beset with some quite serious inconveniences — such as as fact that our ‘island nation’ actually consists of one island plus a sizeable chunk of another one.
Brits have been left asking how much they are prepared to pay for symbolic satisfaction, though the older generation do appear more inclined to dismiss the question, having discerned that it won't be them picking up the tab for their momentary exultation.
And in said tab there lies another distinction between Trump's truculent folly and ours — there’s no way to suggest that the people on the other side are the ones that are going to pay for it.