So everyone that wants to live in London will need to have a job, just like they have today. It's a decent trade-off.
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.
The further London moves away from the UK, the more are cities like Brighton, Cambridge etc. looking more attractive. More attractive to people willing to live in a more mixed area too.
BTW,
>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.
This is already happening/has already happened, unfortunately.