TYB
I dont remember what I was listening to, but someone's SSP story talked about seeing one of those close up, where they could see the people in the window there looking out.
Was doing a search for the Invisible Enemy just to see what comes up and I found this.
https://www.theguardian.com/artanddesign/2018/mar/26/michael-rakowitz-invisible-enemy-should-not-exist-fourth-plinth-winged-bull-date-syrup-cans-defying-isis