I can't remember whether it was a Banksy book or article, but I vaguely recall him saying they/he got away with a bunch of pieces (in particular the designated

I can't remember whether it was a Banksy book or article, but I vaguely recall him saying they/he got away with a bunch of pieces (in particular the designated graffiti walls) by just pulling up in a white van in the middle of the day, wearing high-vis, setting up a tent around their work and getting on with it. No one would question because it was so brazen so there must be authority somewhere. I assume it's probably also how he placed the museum/gallery pieces. Annecdotally reminds me of underage drinking. If you stood with a pint glass at your side looking shifty you got kicked out in 5 minutes. If you were brazenly smoking a cigarette, knocking the beer back and shouting like you owned the place the bouncers just assumed no one underage would draw that much attention to themselves and leave you alone...