WHEN LUCIE BLACKMAN was drugged, raped and killed in 2001, Tokyo’s hostess bar scene was exposed to the world’s horrified scrutiny. Here vulnerable foreign girls such as 21-year-old Lucie were risking their lives selling their company (and who knew what besides) to predatory Japanese businessmen.

Yet when Mo Hayder, an author, heard about Lucie’s death she was astonished. In 1989 she, too, had worked as a hostess in the clubs of the Roppongi district of Tokyo. “It was the safest place on earth,” she says. “I never felt threatened. When I read about Lucie Blackman, I thought ‘what has changed?’ I had to find out.”

Her return to Japan took Hayder to the club where Lucie met Joji Obara, the Armani-wearing millionaire who is currently on trial for her murder. And it inspired her latest novel, Tokyo, a thriller which draws together hostess bar culture, the yakuza mafia and the 1937 massacre of 300,000 Chinese when the Japanese Imperial Army invaded Nanking. It will also make you think hard before taking Chinese medicine.

It is difficult to square this fine-boned, Bambi-eyed, low-voiced woman with her subject matter — the farthest extremes of horror and violence, unflinchingly portrayed. Hayder’s first book, Birdman — a publishing Cinderella which shot from slush pile to bestseller list — featured a serial killer who sewed live finches into his victims’ chest cavities. Her second, The Treatment, is the tale of “the troll”, a psychopath who abducts, abuses and murders boys in South London.

Hayder finds the “cosy crime” of Ruth Rendell and Agatha Christie dishonest: “The whole engine in a crime book is the violent act, yet you never see the violence. That is where I came up with my manifesto, that I was going to describe everything in detail.”

Her fans will not be disappointed by Tokyo. For all its historical research and journalistic endeavour, the novel is a striptease of unfurling horror with a sickening denouement. It features Grey Hutchins, the disturbed product of a sheltered background, who is compelled to visit Japan to find the truth about the Nanking massacre after seeing a grotesque photograph in a book. She is, transparently, an extreme version of Hayder, who grew up in a “bookish, dusty” Essex family with a teacher mother and astronomer father. ITV was banned and holidays were spent “visiting ruins”.

Rebelling against such worthiness, Hayder became a green-haired punk, left school at 15, moved in with a musician and drifted through the next decade doing dead-end jobs and “living off boyfriends”. She decided to move to Japan after seeing Blade Runner and envisioning Tokyo as an escape from bedsitland.

“I had a mad fantasy that I was going to be a geisha call-girl,” she says. “I saw myself in some high-rise apartment with Japanese boyfriends coming round and giving me presents.

“Instead I became a gei-no-nai geisha, which means ‘geisha with no talent’.” In other words, a hostess. Yet the strange thing about hostessing, the thing no one quite believes, Hayder insists, is that it has nothing to do with sex — at least, not the sex act.

The Western girls hired to pour drinks, light cigarettes and flatter the Japanese salaryman after a heavy corporate day are undoubtedly performing a sexual function of sorts, somewhere between the ceremonial geishas and the debt-bonded Filipina hookers at the low-rent “snack bars”. But the only time a customer touched Hayder he was ejected by the mamasan, the club’s equivalent of a Playboy “bunny mother ”. And while, for many, hostessing was a springboard to prostitution, not once did a man ask to sleep with her.

Hayder shows me photos of her twentysomething self, posing amiably with Japanese men. The club, El Manon, looks more like a brightly lit suburban restaurant than a vice den. “What I had to do was no worse than having to be nice to a work colleague in whom you’re not too interested,” she says. “I’d flatter them and say ‘I like your tie’. The number of ties I’ve really loved! I’d ask where they worked, why they were in Tokyo.” Her function was to entice customers to stay, to buy more drinks and to return.

As a white Westerner she was an exotic novelty, consequently her salary was high. The customers were courteous and she dated several of them, including a tall, handsome Korean who, she later discovered, was a yakuza loan shark.

“We’d be going somewhere and he’d have to stop outside an apartment block while I stayed in the car,” she recalls. “But I hadn’t made the connection with gangsters: yakuza to me meant no fingers and tattoos everywhere.”