This photo of the coaling of a cruiser in St Lucia, in the West Indies, in the early 1900s, is an illustration in Unlocking the World: Port cities and globalization in the Age of Steam, 1830-1930, by John Darwin, former Professor of Imperial and Global History at Oxford: the shaping of modern Montreal, Calcutta, Singapore, and other great economic bridgeheads (Allen Lane, £25 (£22.50); 978-1-846-14086-0)