Sometimes, you feel yourself weightless, thinned. You draw back the curtains (if there are any) on a rectangle of wasteland at dawn, and realise that you are cast adrift from everything that gave you identity. Thousands of miles from anyone who knows you, you have the illusion that your past is lighter, scarcely yours at all. Even your ties of love have been attenuated (the emergency satellite phone is in my rucksack and nobody calls). Dangerously, you may come to feel invulnerable.

Long before Christopher Columbus, the celebrated Chinese navigator Zheng He travelled through the south and westward maritime routes in the Indian Ocean and established relations with more than thirty countries in Asia, Africa, and the Middle East.