@paxillin - it was shorthand (I'm on my phone which has no predictive test so everything has to be typed as an individual character) to say that over-crowding in the animal kingdom ends with "violence" and killing. It's not surprising that similar competition for space results in violence also in humans, surely?
The UK is the most densely populated country in NW Europe, and London must be the most densely populated part of the UK. There's over-crowding in homes within that, whether through lack of funds for bigger homes, lack of larger council/HA homes, issues concerning commutes or whatever. So people will be both over-crowded in their homes and their cities, and this places an additional cause of strain on each individual.
Of course, not everyone in shared or over-crowded accomodation is going to turn to violence, any more than they will turn to crime - but it's another exacerbating factor to add to the mix. Plus, you can aspire to raise your family in a home to yourself all you like, but if your minimum wage job won't allow you to afford the rent of a house to yourself, what option do you have apart from a room in a shared house? It's all very well saying that children make you a priority with the council, but if there isn't a home big enough, they don't let you move to one bigger than you have that's still too small for your family's needs.
Waiting lists in London are years long, so now imagine you are the son of that family. It's hard to get peace and quiet, so maybe you blow off doing your homework. You can never get any privacy, so you might as well go out. You can hang out on the street for free, so you do that. You see your dad working all the hours God sends and still not being able to afford a decent standard of living, and you think- "Fuck that, what an idiot" when you've seen how your older "mates" have the latest 'phone or whatever. Just by being runners for gangs/pretty crime/whatever.
Those types of pressures surely play a part also in the crime rate rising, and are also affected by over-crowding and lack of alternatives to solve this.