There are bits of North London that do have fairly high levels of crime - but there's areas like that all over London, often just a street away from much posher, lower-crime bits. Unlicenced taxis are a real problem, with drunk or high people - including many lone women - falling into random, unchecked strangers' cars in the middle of the night when they come out of clubs. When I lived in a shared house in Brixton in South London about 12 years ago, one of the other people there worked illegally as an unlicenced taxi driver. The particular problem with him wasn't that he was setting out to attack women, he just wanted to earn a few quid. But he was a crack addict, who had lost his driving licence due to drunk driving, and his car was untaxed, un-MOT'd and had no insurance, so was horribly unsafe for a bunch of other reasons - and yet there he was in his car outside the clubs every weekend, neatly illustrating how easy it was for totally unsuitable people to get regular taxi work.