I lived in London from 1977-79 and it was a dirty place with the streets strewn with rubbish after market closing on Saturdays. If you went into central London and spent the whole day there in that era the inside of your shirt collar would be black with pollution. Car drivers would empty their ashtrays on the street when stopped at the traffic lights.
Which year was the great London smog which killed 12,000 people?
Gotta be in the 1800's when all those home chimneys were spewing shit into the environment.