[iso1631]

it's expensive because it's mostly nice (although the cheapest place I ever lived in was near west kensington tube station, just on the wrong side of the tracks, but about a mile from kensington gardens.

It's quite clear that you can have housing for 15 million people in the area of Greater London with the density and green space of Westminster.

Does that require grand architecture? Sure. Will it happen? Nope. But it's not a density problem, it's an allocation problem.

Instead great swathes of London are built over with high density semi and terrace housing with a tiny bit of poor green space per person (usually paved over to store a car which sits still 23 hours a day or more)