At least two centuries before Ptolemy and Hipparchus, the Chinese were mapping the sky in extraordinary detail. The Dunhaung chart contains 1,345 stars grouped in 257 asterisms -not for the Chinese a few dozen constellations. The Chinese sky was divided into five great palaces, corresponding to the five Chinese cardinal points. Five? Yes, north, south, east and west, but also and most important, the middle, the Middle Kingdom domain of the Emperor.

Medieval China emerges from this portrait of the Silk Road as an empire that, even at the height of the prosperous Tang Dynasty, was neither monolithic nor unchallenged, a state constantly obliged to cut deals with its neighbours, whose terms its officials then solemnly described as tributes of allegiance.

For centuries, this gloss on China's dealings with its neighbours went widely unchallenged, for lack of other evidence. Stein's burrowing through the latrines, inns and temples of time past uncovered a more complex, less flatteringly concentric, world, one that Chinese archaeologists are now themselves exploring with delight. "It is perhaps provocative", Whitfield writes, to pay tribute to a colonial archaeologist who removed so many finds to India and Europe.

Provocative, maybe; overdue, certainly. It is good to see the gesture so eloquently made.