Interesting that this appears on the front page at the same time as this story: https://news.ycombinator.com/item?id=16828973 I don't have a particular point of view either way other than to say that context matters, and pragmatism matters, and the solution to these potential problems can't be "remove all surveillance" any more than it can be "surveil everything."
But CCTV footage wouldn't have stopped this madness. It would have helped find her body a little more quickly.
In the long term, I guess surveillance would discourage violent crime, as the idea that "they'll see us, the police will catch us" gradually becomes well accepted among people who have the potential to commit crimes. This is probably already true in London, and maybe in other closely-surveilled capital cities.
But even if everyone sane shares the knowledge that "they're watching us", psychotic actors will still do psychotic things.