The Children of Violence made her a radical writer. The first volume, Martha Quest (1952), sets the scene by introducing Martha as a rebellious 14-year-old aware of the political and social evils around her. The second volume, A Proper Marriage (1954), follows her through the disillusionment of an early marriage and her growing need for independence. A Ripple From the Storm (1958) continues Martha's story and also chronicles post-war radical politics.

Then Lessing left it to work on her most famous novel, The Golden Notebook. She does not seem surprised when I tell her I had tried to read it at 12 and abandoned it. Some experience of life is needed to grasp the multi-faceted quality of this extraordinary work, which is in effect a five-way narrative filtered through specific aspects of one consciousness, and within this are the entries from the four notebooks. It is an exercise in social as well as personal history.

In 1965 she returned to the Martha Quest story with Landlocked and The Four-Gated City (1969). By then Martha's story has become far bigger and more apocalyptic. It is true that each of the five can be read alone, but the earlier trio share a cohesion that somehow evades the final two, but then as she points out, "there was a big gap between the first three and last ones". Born Doris Tayler in Persia in 1919, Lessing is the daughter of two victims of the first World War. "My father lost his leg in it and I think his real life ended then, my mother had lost her sweetheart. She met my father when she was his nurse."

Lessing's mother, Maude McVeagh, had never had an easy life. When she was three, her beautiful, flighty mother died. McVeagh, the capable woman Lessing knew as a distant mother and was in constant battle with, lived a miserable existence, always hoping for her dreams to come true. At the end of her life it seems Lessing's mother died only because she felt she was of no use to anyone. As with Lessing, it is all in the autobiographies, and she agrees people are shaped by their early lives. She describes how a child changes once he or she goes to school and is told how to think, "all that wonderful imagination disappears".

Children continue to fascinate her. She seems to fear for them in the world. In The Fifth Child, Ben Lovatt's birth proves devastating for his parents who had set out as a young couple to create an enviable domestic paradise. Into the increasing pressure of a home with four small children, comes a child whose stormy period in the womb acts as a prelude to what is to follow. That novel is on school courses in Italy; she says of Ben, "he is a throwback to something" and expresses her concern about the number of young people who identify with him.

"I have been at readings when young things of 17 will come up and announce, `I am Ben'." It is terrifying and also an example of the individual at odds with the world and something she understands. The new novel is very good and has achieved the always difficult task of being a strong and convincing sequel. In it Lessing has managed to allow Ben, the destructive child monster of the first book, to become something of an innocent. "He has learnt the rules," she says.

It was her German publisher who had suggested the sequel. The Fifth Child has been very successful there. It is a visionary book and one which will last.

The small, grandmotherly figure with her hair pulled back into a severe bun was once an impatient young woman, an individual Lessing's readers will never lose sight of. Freedom of choice, the individual in society and, above all, moral responsibility are her themes. But there are other factors as well. Lessing confronted the dilemma of responsibility and survival. At the mention of Doris Lessing, there are those who will jump in and declare "but she left her small children". For her there was no choice, as she writes: "The fact is, I would not have survived. A nervous breakdown would have been the least of it. In the four years I was married to Frank I drank more than before or since. I would have become an alcoholic, I am pretty sure. I would have had to live at odds with myself, riven, hating what I was part of, for years."

Her childhood as a child of English parents living an English life, albeit an impoverished one, in Africa sounds miserable. One of her first discoveries was her mother's obsessive love for Lessing's younger brother. Frustration and exasperation were soon familiar to her and it suggests the origin of not only the tone but the humour of her writing, particularly the first three books of the Children of Violence series.

Before she was eight, she was sent to a convent school where she would spend four long years: "Eternity," as she writes. "I used to wake up in the morning with the clang of the bell and not believe I would live through that interminable day until the night. And, after this endless day would be another." As a Protestant she frankly admits to be terrified of the strange Catholic rituals. She was clever, yet illness and a subsequent long stay at home ended her formal education at 14.

With the end of her schooling, came the end of her childhood. She worked at various jobs, including that of nursemaid, shorthand typist and telephone operator in Salisbury. While she cringes at the word "wise" which she says was often applied to her, she understands the worlds of girls and women so well. Yet Lessing is writing about life as lived, as much as about a woman's life. It has often been pointed out that her characters are not particularly loveable. This is due to their being real.

As a young girl alert to romance, Lessing married Frank Wisdom, 10 years her senior, more out of a feeling that this is what she should be doing. A mother at 19, a second baby soon followed, and Lessing, though in a new life, was still encountering the restlessness of the first. She became involved in progressive or radical politics. "I was a Red," she says in that singular way she has - offbeat yet exact. It is all described in A Ripple from the Storm, the third and probably the most autobiographical of the Children of Violence quintet.

After divorcing Wisdom she married Gottfried Lessing, a Russian-born German who could assume either nationality depending on his mood. It was not a love match, but a baby, her third, was born in 1946. They parted, or rather drifted away from each other. Her slow drifting away from communism took longer.

By 1954 she was no longer a member of the Communist party. "But it was not until the early 1960s I ceased to feel residual tugs of loyalty." The psychological make-up of the writer makes it possible to achieve the sense of distance. But at various times she suffered painful emotional loss.

Lessing has never played for sympathy. There were several relationships, one in particular, which lasted for four years. Lessing was committed to the man, who was married, and she grieved when he left her. There was also the leaving of her first two children. Her son John died some years ago; her daughter Jean and son Peter are still alive. Her relationship with her mother was a tragic stalemate. As she says, her life is in the autobiographies.

It is, as is so much more. They offer a portrait of the times. But her life, and certainly her feelings, beliefs and fears, have always been evident through much of her fiction. Lessing's world is a woman's world down to the hurt felt on hearing her lover remark, as she records in Walking in the Shade: "You share more than you know with my wife. She's got the same wallpaper in her kitchen." Lessing adds: "In those days there wasn't so much choice as now . . . so this was not really so surprising. But deflating, yes."

Lessing will be 81 in October. Aside from complaining about a stiffness as she stands to go to the kitchen for more tea, she does not seem old. "I don't have the energy I used to have. I used to have such energy," with more surprise than regret in her voice. Asked how she feels about age, considering how well she has written about the cruelty of ageing, she says: "Well when you've lived it, I don't mind particularly."

Did she expect her life to take such a course on arrival in England with a small child and manuscript in 1949? "Well no one told me it was impossible," she says with a smile. "Perhaps if they had . . . "

Doris Lessing will read from her work and is in conversation at the National Gallery next Thursday, June 15th, with Theo Dorgan, as part of the Dublin Writers' Festival which runs from June 15th to 18th

Ben, in the World is published by Flamingo at £16.99 in UK