Books: The Books Interview: No more fog on the Tyne

What sort of woman exposes the dark secrets of Britain's best- loved author? Kathleen Jones talks to Clare Colvin

In her later years, Dame Catherine Cookson reached the status of national treasure. She had written 97 books by the age of 91, raiding her own life for her fictional heroines - warm-hearted, doughty women from impoverished northern backgrounds.

It seemed all a biographer had to do was re-tell the life aired so often in the author's work. So it appeared to Kathleen Jones at first. She had written three literary biographies, was about to begin one on Katherine Mansfield, and was visiting South Shields at the time of Catherine Cookson's death in 1998.

Kathleen Jones's grandparents were, like Cookson's, working-class Tynesiders. Jones's grandmother was born one of 12 children in a three-roomed house on the banks of the Tyne. With the knowledge of her inherited background, and of Cookson's books, which she had discussed with her women's study group, a biography on Cookson called. Her publisher paid her a modest advance, and she set to work.

It was only when she interviewed a retired professor from Newcastle University that she felt a sensation, like a dowser, of something hidden under the well-worn story. Catherine Cookson had told the professor, researching a thesis on autobiographies, that she had written eight drafts of Our Kate, the autobiography in which she ostensibly revealed all, facing up to the shame of her illegitimacy. Eight drafts from a famous author who was easily completing two or three novels a year? It sounded like the dance of the seven veils in reverse.

Through the Internet, Kathleen Jones ran the early drafts to earth, undisturbed in the University of Boston's archives. She had already spent her advance on research in Newcastle and Hastings, so the American trip went on to her credit card. The papers were unread, among them a box of very early hand-written pages, dating from 1946 to 1958. The book which became Our Kate had been originally titled From the Seed of All Sorrow. And the papers revealed Cookson's life to be far darker than anyone could have dreamt. Jones had two conflicting emotions: first, how marvellous to discover this, and then "this is like being given a hand grenade with the pin out".

The impact has erupted with the Mail on Sunday's serialisation of Jones's book, Catherine Cookson: the biography (Constable, pounds 16.99). First came details of Cookson's lesbian relationship with an obsessively jealous laundry worker, Nan Smith, and its effect on her marriage years later. Then followed the revelation that Cookson was brought up in an abusive home. Her mother, Kate, was sexually abused by her stepfather and stepbrother. In her turn, Catherine may have been sexually abused by her own mother. It would, Jones argues, have been the reason for Catherine's lifelong hatred of her mother, for her hints of "things so terrible" she could not write about them, and for her ambivalent feelings about having a child after she was married to Tom Cookson.

When I met Kathleen Jones, the flack from the serialisation was uppermost in her mind. Maybe she was naive, she said, but she had had no idea that her careful biography would simply be gutted for salacious bits. In the book, the reader arrives at the dark secrets in stages, rather than having the whole thing flung onto the page in a few thousand words. She joked about Cookson fans taking out a contract on her.

The advance was, like her previous advances, small. Serialisation had changed that, being comfortably in excess of the six-figure mark. The first thing the money will go on, apart from paying off bills, is repairing the roof under which she lives, at present revealing gaps of sky and ivy roots.

She has shared the old mill house built against the cliff banks of the River Eden in Cumbria with her partner, sculptor Neil Ferber, for six years. During heavy rain, the ground floor, where the sculptures and pottery are exhibited, is flooded when the river pours through the window. There has been a mill here since before the Norman conquest, and this building has existed since the 18th century, so they are not unduly worried about being swept away. When we met the sun was shining and we sat out on a terrace. On the cliffs opposite was Appleby Castle: a scene from an 18th- century painting.

Kathleen Jones began writing poetry and stories as a child on her parents' hill farm in the Lake District. She married before she was 20, had two children, studied law, then took a degree in English at Bristol University. For 11 years she lived wherever her husband, a civil engineer, was posted, in the Middle East and Africa. When the marriage ended, she returned to England with her four children and worked as a freelance journalist and women's studies tutor.

Her first biography, on Margaret Cavendish, Duchess of Newcastle, evolved from a play written for Radio 3. Her second was on Christina Rossetti, her third on the wives, sisters and daughters of the Lake Poets. With this book, the acclaimed A Passionate Sisterhood, Kathleen Jones came across the industry surrounding famous dead writers - though the fact that Wordsworth, Coleridge and Southey were rotten to their womenfolk doesn't seem to have reduced visitors to Dove Cottage.

"I feel ambivalent about writing biography," she admits. "There is a slightly voyeuristic element, as if reading the work of an author is not enough. We want to know the intimate details, and I am not sure whether all of it is relevant to the work... Yet at the same time biography is a respected art form in its own right with a much longer history than that of the novel, which started as fictionalised biography. The lives of writers do illuminate their work and how they came to write it.

"Both biographers and tabloid newspapers dig into people's secret lives. It's a bit like the difference between archaeology and tomb-robbing. They are both doing the same thing, but with different motives. The tomb robber takes for monetary gain, but the archaeologist is interested in every detail of the life and what we can learn from it."

The papers in Boston University filled in some gaps but left others. Jones had tried unsuccessfully to find Cookson's first literary agent, John Smith, who she was told was either dead or living abroad. Then, after she had completed the first draft, she went to Cookson's memorial service. As the congregation filed out, she heard someone ask an elderly man "Are you John Smith?"

Smith had once attempted to write a biography of Catherine Cookson, recording hours of interviews. When Cookson saw the result, she withdrew permission for publication. Now he magnanimously gave to Kathleen Jones the tapes he had been prevented from using. They filled in more gaps on her relationship with Nan Smith and "the dark secrets and terrible torments" inflicted on her by her mother, although Cookson never completely came out in the open. So is it only a biographer's guesswork?

"I didn't come to this conclusion lightly," says Jones. "I undertook a great deal of research on mother-daughter abuse. Catherine looked on her step-grandfather and uncle with affection, and all her hatred was directed against her mother. Something had traumatised her and left her maimed. She tried once more, at the age of 89, to write about her mother `warts and all', and suffered another nervous breakdown."

The Catherine Cookson industry is huge and thriving. The money from all rights amounts to many millions a year - a staggering sum from one woman's writing. There are new books in the pipeline. In October, Transworld publishes A House Divided and next year Kate Hannigan's Girl, the sequel to Cookson's first novel. The manuscript, taken from the bottom drawer, will be her 100th published work.

Kathleen Jones is aware her own book is not welcomed by the author's estate. But she is also sure it is a story Cookson wanted told, if only after her death. In the tapes, Cookson said she wanted it to be known how badly she had been treated. After her death, Tom Cookson, who died three weeks later, destroyed 17 years of her diaries and the correspondence with Nan Smith. She left the clues, though she could not face the writing. What should the biographer do, asks Jones: walk away from material that cast new light on Cookson? If anything, it makes her an even more heroic figure.

Before I leave, she plays one of the tapes. We are sitting in the attic where she writes, overlooking the mill race. The rich warm voice of Catherine Cookson, with a musical Irish inflection to the words, tells of how after her miscarriage, she was afflicted with such a strong feeling of aggression when she saw at baby in a pram outside a shop that she wanted to dash it to the ground.

In order to control her impulse, she went into a bric-a-brac shop, where she picked up a small ginger jar. The beautiful thing in her hand soothed her, and she bought it. The incident sounds like a perfectly formed short story, and in the telling, Catherine Cookson sublimates her pain.

Kathleen Jones, a biography

Kathleen Jones was born in 1947 and brought up on a hill farm in the Lake District. She took a degree in English and Medieval Studies at Bristol University and spent 11 years in Africa and the Middle East, returning to England with her four children. In 1988. her first biography was A Glorious Fame, about Margaret Cavendish, Duchess of Newcastle, followed in 1991 by Learning Not to Be First, on Christina Rossetti, A Passionate Sisterhood: the sisters, wives and daughters of the Lake Poets in 1997, and now Catherine Cookson: the biography. She has written short fiction, journalism and a collection of poetry, Unwritten Lives (Redbeck Press). Kathleen Jones lives in a mill house in Cumbria with her partner, the sculptor Neil Ferber, and writes full-time, working occasionally as a writing tutor.