In 2003/4 – the year is not mentioned in his book – the renowned travel writer Colin Thubron made a tough, 7,000-mile, eight-month trip from central China to Turkey. (The Afghan portion, delayed for a year because of fighting, is included seamlessly here.) Travelling largely by bus, rickety taxi and train, with stays in bottom-grade hostels and hotels, he ate revolting food and was occasionally in danger. The SARS epidemic had driven most tourists away and he was constantly having his temperature taken by police doctors; at one point he was warned that in two weeks he might be dead. I have made the same trip up to the western borderlands of China by the same means, and remember with a shudder the transport and the places to stay. 

The Silk Road, these days a tourist industry come-on, is a term, as Thubron says, that was devised by a nineteenth-century German geographer. But such a thing did once exist, meandering for 6,000 years over different routes from China as far as the eastern Mediterranean. Chinese silk appeared in Iron