You have to look at how you can manage London, not plan it. How you can treat it, if you like, as an exercise in gardening, look at which plants are thriving and which aren’t. Weed out new plants and try new species, encourage those that are doing well. Sometimes try to corral them so they don’t do a Japanese knotweed and take over the whole garden. But at the same time recognize the local climate and ecology and work with it rather than against it.
