I remember going to Sheffield in it's muckier days. Went round English Steel Corp about 50 years ago when I was doing my HNC in Prod Eng. I've never seen such heavy engineering equipment before or since. My wife's uncle ran the Playhouse Theatre, Sheffield, and they couldn't hang washing out in the open as it came back in with holes through it. When I pass by these days, on M1, it looks quite clean.