That is incorrect, London is not like that today. London is an extremely multi cultural city, with both rich and poor living side by side in the same boroughs. A lot of people argue that most of London's unique culture in places like Brixton came from the poor and that's what made London in a lot of ways great.

If you say, everyone in London will need a job, then you are then moving the poor / unemployed on mass out of the city. On paper this may look great, but for social-economic reasons this is a disaster.

You would end up with a 'walled garden' of elite living in London and the poor / unemployed living outside. The city would lose it's unique cultures, become even more gentrified / elite than it currently is and social unrest could start to occur.