London basement extensions as normal as loft conversions, study finds

Most are built for affluent professionals rather than oligarchs, with trend raising flood concerns

With their underground swimming pools, cinemas and art galleries, London's luxury basement developments have long provoked envy and disgust as depositories for the hidden wealth of the super-rich.

But a study that has mapped all the 7,328 basements approved by 32 boroughs and the City of London between 2008 and 2019 has found that the majority of these developments were built for affluent professionals rather than oligarchs, with the researchers saying they have become as normal as loft conversions.