Few crime writers can claim the dubious distinction of having seen a man shot dead before them, but then nothing about this woman's existence has been ordinary. Poverty, madness, attempted suicide and sudden violence pock-mark her past like exploded shells, but her efforts to make sense of it all have produced three of the best British crime novels of the last decade. Julia Wallis Martin - novelist, mother, wife and somewhat unfortunate person - this is your life. Given the nature of her experiences, it would not be a total surprise to find Julia Wallis Martin wheeled into the busy London restaurant under some form of medical supervision. It is therefore a surprise to encounter instead a vivacious, pretty blonde, now 43 but looking a good deal younger and a great deal happier than her history might lead one to expect. If, as Graham Greene once said, childhood is the bank balance of a writer, then Wallis Martin was unusually generously endowed and has plundered her account wisely. Her roots were originally Irish: her great-grandparents came from Cork and Northern Ireland respectively, but emigrated to England and set about shaking off their working-class roots. By the time Julia's mother, Josephine, was born, the family had become property owners in the Midlands and a safe, middle-class existence was assured for their daughter. But Josephine had other plans. "Like all newly middle class people, if they sensed the possibility that a member of the family was about to blow it, they'd turn on them quite viciously, and that's what more or less happened to my mother," Wallis Martin explains. "She blew it by behaving in a manner that completely appalled the rest of the family. I mean, in the 1940s she ran off with a married man. In the 1950s, while she was married to the married man, she ran off with another married man and consequently she was ostracised by the rest of the family. They were not bad people. They were just a product of their time." Josephine was 18 and a member of the Land Army when she met Arthur Gibson, a session musician with the BBC who was already married to a chorus girl. Josephine promptly deserted to run off with him, quickly became pregnant and gave birth to a girl, Jan. It was, says Wallis Martin, "a miserable marriage. He was an alcoholic and was constantly out of work. She stuck it out for 11 years then ran off with my father (a wealthy farmer named Walter Martin). She abandoned my half-sister and didn't see her again until she was in her 20s, didn't even try to see her again. In later years, it became obvious she was a manic depressive and she was very ill at the time, so that did have an effect on the way she ran her life. She just lurched from catastrophe to catastrophe." For a time, catastrophes were averted while Julia lived with her mother's parents. Unfortunately, Josephine decided once again to shake up her life and moved herself and her 11-year-old daughter to a council estate in Warrington. "I ended up living in a very dreadful council flat on a very dreadful estate in the north-west of England with a suicidal, manic-depressive mother. And the effect was to make me think that I didn't want to be in this situation for the rest of my life and to wonder how do I avoid it, and what do I do with my mother?" Josephine's illness grew steadily worse: one afternoon, Julia returned home from school to find an ambulance waiting to take her mother to hospital following a Lithium overdose. At this point, Wallis Martin laughs at the near-gothic horror of it all. "It got to the stage where she couldn't walk, couldn't function normally, and I found myself trying to cope with this woman at a time when a kid needs all the help she can get just to keep it together. I had two choices: I could either be confused by the situation or take a very cool look at it and decide: how do I get out of this?" Fate intervened to make the decision for her: Josephine died of breast cancer shortly before her 50th birthday, leaving the 17-year-old Julia homeless. The council gave her a flat, but she occupied it only briefly. "I remember looking out of the window and thinking, `I have to walk away.' "What was I going to do, stay in Warrington for the rest of my life because someone had given me a place to live? I just had visions of myself in 40 years still living in that building . . ." She moved to Oxford, worked as a waitress, and wrote. Over the space of five years, one short story was published out of countless stories submitted. But at this point, a kind of veil is pulled down over Julia Wallis Martin's life. There is a period of some seven years about which she simply will not talk to the press, years shadowed by bereavement. She plans to write about them for her son and will allow him to choose, when he is old enough, whether or not the account should be published. Until then, the subject is very much closed. Thankfully, this being a life not short of incident, there is a great deal of other material to be getting along with. At the age of 27, Julia married Chris, a banker 15 years her senior, and moved with him to South Africa. They were planning to stay for six months but ended up staying for seven years, during which time Wallis Martin worked as a commissioning editor for a publishing house and published two books of her own: a biography of the South African showjumper Gonda Betrix entitled, somewhat unfortunately, Gonda Betrix: Jumping to Success, and a novella, Mary Hibbert. "We lived in Johannesburg, in the archetypal property with 12-foot high walls and razor wire. I kept begging Chris to leave South Africa, but he was having a fantastic time. He was one of these guys who, like a lot of men, are capable of going into complete denial. It was a case of `this violence is not happening around me. Okay, maybe it is, but it will never happen to me. Okay, maybe it will, but I can handle it if it does.' "Famous last words . . ." In the space of six weeks the family and their baby son, James, were the victims of two attempted armed robberies in their home, a robbery at gunpoint in a restaurant, and Wallis Martin had her car hijacked by gunmen at a roadblock. The final straw came when gunmen tried to enter the house during a dinner party. The guests were four armed Afrikaaners, all of whom had done their military service in Angola. The first gunman was killed in the hallway of the house while baby James slept upstairs. Another was shot on the patio.

IT was the end of the marriage. Within 24 hours, Julia and her child were on a plane back to Oxford. Forced to live in cheap, rented accommodation, she turned to writing to support them. After a number of rejections, her first novel, A Likeness in Stone, was published in 1998. Beginning with the discovery of a young woman's body in a submerged house beneath a reservoir, it examines the history of a group of former college friends and their involvement with the victim, and marked the arrival of a spectacularly accomplished crime author. A Likeness in Stone, which was filmed, somewhat unsuccessfully, by the BBC, was followed by The Bird Yard, a novel which drew its central conceit from an incident in Wallis Martin's childhood. "When we lived on the council estate, my bedroom window looked out on a row of derelict houses. "Someone had moved into one of those houses. He had attached mesh from the garden fence to the top of the house, opened all of the windows and he had filled the garden and the house with exotic finches, so the house was an extension of the aviary. Of course, the local kids were absolutely fascinated. He was a paedophile under 24-hour surveillance, which we didn't know at the time. He always had sweets - I remember being given sherbet fountains - and he would let the children hold the fledglings . . ." Her third novel, The Long Close Call, is radically different from its predecessors. It tells the tale of a policeman, the son of a jailed criminal, who kills a gunman during a bank raid and finds himself being hunted by the family of the dead man. Once again, it was inspired by an incident from Wallis Martin's own life: an encounter with a former boyfriend, the son of a convicted bank robber, who had become a policeman. "His father had been inside for GBH and armed robbery, so he'd committed fairly serious crimes, but he was actually a rather quiet, shy man. "He was a very dark character, and his son was very similar. He probably made a very good cop." Now happily remarried - to Russell, a screenwriter - her new-found contentment seems to have allowed her to draw on the events of her past by giving her a sense of security in the present. Her fourth novel, Dancing With the Uninvited Guest, will be published later this year, and The Long Close Call has been optioned for television. The scars from her past have not entirely healed - she has poor short-term memory, trouble with figures, and, she half-jokes, she has even read up on manic depression in case she starts to display the symptoms shown by her mother - but those scars have made her what she is: a gentle, sensitive, funny woman and, not least of all, one of the best female crime novelists currently writing.

The Long Close Call is published by the New English Library (£5.99 in the UK)