Some 33m people live in the Tokyo metropolitan area. That is roughly one Texas, half a Thailand or five-and-a-half Denmarks. But it is no longer the world’s biggest city. Good. For too long Tokyo served as a kind of teleological endpoint of urbanisation: the megacity the rest of us can aspire to. Humbug! In truth, most people in megacities live in dysfunctional, polluted, gridlocked sprawl. Many of these places can barely provide clean water or air, let alone the sort of sanitary standards that allow for the consumption of raw fish.

In my day job covering India I spend a lot of time trying to figure out why its cities are such—let me be plain—civic catastrophes. So when I learnt last month that Tokyo had been displaced by another megacity, I wanted to see whether the lessons from India are generalisable. Alas, they are. Each megacity is unique. But the things that cause them to fail are not.