It can often seem a triumph that India exists at all.

By some miracle of human ingenuity and industry, a land area barely bigger than Argentina with less water than Colombia is able to support nearly a fifth of the world’s population. The recent scorching temperatures in the capital New Delhi are a warning sign, however. The magic spell that has sustained this achievement is coming close to breaking.

That is an issue not just for those sweltering on the streets of the world’s second-biggest city, but for the path to wealth that 1.4 billion people hope to follow.