No it's wrong, and dreaming of a world that has passed.
To ask a policeman to wander around West Croydon, Brixton etc, at 2am, alone, is plain irresponsible unless he (or she of course) is armed. I wouldn't do it, and neither should he/she. Pairs is much safer. I would feel equally comfortable approaching two policemen as one.
I expect there is some potential money-saving going on here.
Personally, I wouldn't police areas like West Croydon, Brixton, at night. Fence them off, let them get on with their local tribal slaughter, then hose down the streets in the morning.