After visiting London

Two guys begin to smoke.
Recently I was in London. You know what, such a clean city!
Really?
Yeah! I light up a cigarette, and then a local policeman comes to me and asks to put it out. I throw it away, he moves away, I begin to smoke the new cigarette. Then another cop approaches me: Put out your cigarette, please! I throw it away again and the story repeats.
And what next?
What-what!!! It turned out that there are 1684 cops in London!