In his latest work, writer John Man focuses on a general who is probably as relevant today as he was nearly a thousand years ago, when the Silk Road linked China to the Islamic world. Andrew Moody reports.

John Man, a leading writer on China, is unconcerned about being described as a popular historian.

His books, which include biographies of Marco Polo and Genghis Khan, and have a trademark light jaunty style, sometimes sell in their hundreds of thousands.