Around 1690, a few officers of the British East India Company in Bengal decided to find a convenient and safe settlement for trade; they chose the spot where the city of Calcutta would emerge. They needed to be near enough to the sea and far enough away from the Mughal provincial capital and administration in the interior, with which the Company maintained an awkward relationship. The chosen location had the advantages of being on the right bank of the Hooghly (the more navigable part) and suitably distant from the Mughal bureaucracy. It was also sufficiently inland to be sheltered from the tsunamis for which the northern Bay of Bengal was famous.
A hundred years later, this place did not seem so great. The founders of Calcutta almost certainly did not imagine that the settlement would grow into a city of more than a 100,000 people in 1750, and 500,000 in...