This seems pretty silly to me. 30 story blocks of flats tend to be prevented by the planning permission system (potentially before they are proposed as developers may know what won’t succeed) which is roughly a combination of local government and local residents. There are other things which may make building difficult – historical preservation (eg listed buildings) applies to much of the more central parts of the city, construction can be expensive, etc.

Perhaps the real London elites are the clay underneath the city which makes tall buildings more expensive.