The person who put Boucher on his current track is an old friend in Guangzhou, a seasoned French sinologist who not only encouraged him to write, but who also inspired the queenly heroine of his first three novels, Reine Fermont.

So why did he choose a female protagonist? 'Why not?' asks Boucher. 'The crime genre is simply a way for me to talk about the things I find amusing in Guangzhou, both the city and the people I know there. Reine is a strong personality who, while being an undisputed expert on all things Chinese, can't help sticking her nose into other people's business. But she's also a homage to this woman I admire.'

Yet for all his love of discovery and surprise - 'Adventure is not knowing what's going to happen to you when you wake up in the morning', he says - Boucher started his working life as a bureaucrat. Trained in law and political science, the 45-year-old served in Brussels for 10 years as an assistant deputy at the European Parliament and as director of an EU consulting firm. His adventures began in 1994, when he saw an advertisement in French newspaper Le Monde for Putonghua courses on the mainland. He enrolled at the Guangzhou Institute of Foreign Languages, and has called southern China home ever since.

Along the way, Boucher has accumulated his share of Chinese names: Fang Suo (Francois), which he uses on his business cards; Xiao Lajiao (Little Chili), because he likes it hot; as well as Fan Tong (Rice Bucket), which mocks how his slight frame masks his 'bon appetit'. His first two novels (Le cheval celeste and Le livre des fermentations) have been translated into Chinese, under a single title: The Assassination of the Consulate General, published by Hai Tian Shenzhen in 2003.

The book might have gone relatively unnoticed on the mainland, if not for a sensitive reader who complained to censors that the author had defamed his Guangzhou neighbourhood. Concerned that Sino-French ties might be damaged by such an irreverent work of fiction - in which the French consulate-general in Guangzhou is assassinated by a Chinese citizen - officials banned the thriller. Police raided bookshops in Guangzhou and Shenzhen to confiscate the offending paperback. Fortunately, the publisher put the book back on the shelves.

Boucher had always had a love of trains, but it wasn't until a friend recommended him to a railway journal, La Vie du Rail, that he set his first story on the tracks.

His journey of discovery into the Yunnan railway began in the south of France in Aix-en-Provence's Centre of Overseas Archives. After scouring the records of the French colonies, Boucher returned to explore what was left of the narrow-gauge mountain railway 95 years after it was built to exploit the tin and other natural resources in the mainland province and tap its trade potential.

'Many stations have kept their original French architecture,' he says. 'You'd think you were in Normandy or in Auvergne, except that your fellow passengers are Miao people dressed in striped costumes.'

The French apparently left more than the railway tracks and train stations. 'You see a lot of Eurasian faces,' says Boucher.

'Once, I saw a local ticket collector who looked like me. I thought I was looking in the mirror. He obviously had the same reaction, because he turned away and never collected my ticket.'

Thanks to his thorough research, Boucher now has at least one friend to visit in almost every village along the railway. Among them are a pharmacist, the ladies who lunch at the school canteen in Bai He, and countless policemen, locomotive engineers and station chiefs. But a recent journey to see his friends on the Yunnan route proved difficult: foreigners are now forbidden to board the increasingly decrepit train 'for safety reasons'.

This year Boucher settled in Hong Kong and set up an information agency, writing articles for specialist French publications on topics including law, insurance, patrimony, wine, urban transportation and, of course, trains. His next novel is set in what is now the port of Zhanjiang in southern Guangdong, once a loosely defined territory without natural resources that was leased to France in 1898.

'While the British had Hong Kong, the French had Fort Bayard,' says Boucher. 'It's the perfect subject for a novel: this place that's completely forgotten today, that didn't officially exist, that never became anything.'

Again, rail tracks figure prominently in the book. Not only will it be published by La Vie du Rail, but the story is built around a fictional train inspired by the old Decauville portable railway in Laos. 'Once I introduced the train into the story, everything fell into place,' Boucher says. No matter that Fort Bayard was never traversed by a locomotive. 'In novels, anything is possible,' he says.