His own odyssey allowed Leffman to retrace Mesny's seemingly endless treks, visiting the places he fought or lived, and interviewing direct descendents of many of his friends and colleagues.

He also set great store in the Miscellany as a source of information about his subject's opinions of the people and events he encountered during nearly 60 years in the country.

As Leffman points out in the introduction to The Mercenary Mandarin, the Miscellany, written in the flowery English of the time, is an extraordinary piece of work, given that Mesny left school at age 8 and his English was initially poor. As Channel Islanders, and therefore geographically closer to France than the British mainland, the Mesny family spoke French at home.

Mesny's life has many parallels with modern China, according to his biographer. "Then, as now, China was opening up to the rest of the world after a period of isolation, and everybody - both foreign and Chinese - was jockeying for position, trying to stay ahead of the curve and milk political and social changes for what they were worth," he said.

"As in the West, I think Chinese specialists have come across Mesny, though I don't think there's any public awareness of his exploits. But there's an increasing interest in the foreign view of China, especially during the 19th century. It's also clear that Mesny had an influence on the career of Zhang Zhidong, China's first industrialist. With a new museum dedicated to him opening shortly in Wuhan, there's an opportunity to explore their relationship."

Leffman has now decided that it's time to close the book on Mesny and concentrate on something, or someone, else, and is juggling ideas for a new project: "At the moment I'm wavering between a couple of ideas - one a history, the other fiction - so watch this space!"