I think a good chunk of it was probably installed as a consequence of terrorist attacks during The Troubles[1], which led to the "Ring of Steel"[2], a fortified

I think a good chunk of it was probably installed as a consequence of terrorist attacks during The Troubles[1], which led to the "Ring of Steel"[2], a fortified security/surveillance cordon around the financial districts. If you compare those measures to the US response to Sept 11th and others, I think you'll find a lot in common. I think at the time the measures were widely welcomed by the public too, although I'm not certain. [1] https://en.wikipedia.org/wiki/The_Troubles https://en.wikipedia.org/wiki/The_Troubles [2] https://en.wikipedia.org/wiki/Ring_of_steel_%28London%29 https://en.wikipedia.org/wiki/Ring_of_steel_%28London%29