WHEN the novelist Rose Tremain was ten, her father, the unsuccessful playwright Keith Thomson, abandoned his family to live with his mistress. Their thin, anxious mother Jane’s life in ruins, Tremain and her sister, Jo, 14, were packed off to a positively penitential girls’ boarding school, Crofton Grange in Hertfordshire -- “a rural prison”.

“Our father didn’t love us any more; he loved someone else. We just had to bear it,” writes Tremain in her memoir, Rosie: Scenes from a Vanished Childhood. A book she thought she would never write, it is as outstanding as her 13 novels, from Booker-shortlisted Restoration to her most recent, the multiple award-winning The Gustav Sonata, and five short story collections.

With her daughters cast away from idyllic summers at their grandparents’ country house – where they felt “drugged with happiness” – and comforting nursery teas at home in Chelsea with Nan, their adored nanny, Jane embarked on a love affair with her husband’s cousin, Sir Ivo Thomson, whom she later married. Ivo’s wife began sleeping with the husband of a close friend. How they contrived these adulterous affairs, in plain sight of each other, Tremain, 74, has never worked out – “but it was as if abandonment became contagious”. The grown-ups in London had entered “a period of sexual madness... playing musical beds”.

Several years ago, Tremain, who was made a CBE in 2007, was told how the mother of a fellow pupil witnessed a distressing send-off at Liverpool Street station where the stick-thin boarders assembled for the train taking them back to the eternal cold and low-calorie diet. Jane and the mother of Tremain’s best friend dutifully kissed their daughters, “ignoring any weeping that might be gathering in us, then, before the train had left the station, linked arms and turned away, saying, ‘Good! Now we can get on with life!’”

Educated at the Sorbonne and the University of East Anglia, Tremain, who has one daughter, Eleanor, from her first marriage and two grandchildren, Archie and Martha Rose, has rarely drawn from her own life in her fiction, but this image had great power in her mind. “I didn’t witness it but I can see it and hear it very clearly. In order to exorcise it a little and to make it less painful to me, I used it virtually verbatim, in a short story called The Closing Door in my collection, The American Lover. In the story, I punished the woman who is most like my mother. I took her husband away from her and left her with an unknown future.”

This is just one of several insightful “vertical footnotes” – her renowned biographer partner Richard Holmes’s description – in her memoir revealing how she has occasionally used incidents from her loveless, upper-middle-class childhood in her fiction. Although, given the fact that her childhood was shrouded in secrets and lies, it is astonishing that she has not used more of her life story. For instance, her mother was raped by two servants during her second marriage, a shockingly mysterious event that Jane never discussed. And her father, the failed writer, eventually joined a cult. We agree when we talk down the line – Tremain is snowbound at home in Norwich, where she has lived with Holmes for more than 25 years – that her father was “a s**t”. Her relationship with him was “agonising”. The sisters saw very little of him when their parents were still together and had no real idea who he was. He almost never took them anywhere or played with them on their own. “Our access to him was rationed.”

He would make rare visits to the nursery and read his daughters’ comics aloud. The names of the characters amused him: Belle of the Ballet; Lettice Leefe, the Greenest Girl in School. (Rosie is full of nostalgic references that will open up Proustian pockets of memories for readers of Tremain’s generation -- those whose first lipstick was Max Factor’s Roman Pink -- although she hopes it will strike a chord with younger readers too.)

Years later, she sent her father a copy of her extraordinarily prescient,

best-selling 1993 novel Sacred Country, about a young country girl called Mary who becomes a young man called Martin. A brilliant novel decades ahead of its time and about to be reprinted in a 25th anniversary edition, the book was returned unread. She says that, as far as she knows, none of her subsequent novels was ever read by him.

After insisting over the years that we have all had enough of memoirs, what prompted her to write Rosie?

“My daughter Eleanor is a psychotherapist. We have wonderful ongoing conversations because there is so much common ground between writers and therapists. One day we were talking about my distant past and my childhood – she knows about my grown-up past since she remembers a lot of it. She said, ‘Mum, I would love to have some sort of record of these things. Otherwise, they are going to slip away and we’d never know about them.’ That conversation got me thinking something I hadn’t thought before because you are right, I haven’t drawn on my life very much in my fiction. Perhaps if this younger generation is interested, I thought, then it might be worth trying to set some of this down.

“I got out old photograph albums – they tell you so much. I also went through a box of holiday snapshots which I’d taken from my mother’s house after she died but never opened. [Tremain’s parents both died in 2001.] In the bottom of the box there was a large photograph, face down. When I turned it over it was in pristine condition and it was a picture of my father which my mother had kept hidden away all those years when she was married to Ivo. Secrets and lies... My childhood was full of secrets so I thought it would be interesting to write about. And, yes, I do think that despite everything my father was the love of Jane’s life.”

Does she agree with Holmes that “Autobiography is a perilous enterprise? It is. People have been asking if I will go on to write about my writing life. No, I will not. I wanted to capture that childhood. I do not want to do the perilous bit at all. It just isn’t that interesting anyway. If I had had a flamboyantly exceptional life, I might be tempted. But I haven’t and I would not want to hurt some people who have been in my life.”

Despite the privations of Crofton Grange, Tremain’s greatest fount of consolation was her Brodiesque English teacher, Miss Robinson – “Robbie” – the school’s only true intellectual who treated her girls as “clever” children, making Shakespeare thrilling and taking them to meet her friend, the Poet Laureate John Masefield.

Although Tremain did not publish her first novel until she was 33, she always knew she would write after a summertime epiphany when she was about 13 or 14. Alone after a tennis game, walking under a coral sky in the school gardens perfumed by a nearby hayfield, she was filled with a profound feeling of wonder. How could she capture this marvellous moment? How could it become new again? Only by writing about it. If she did not write, she knew then that her life would be only half lived.

Tremain has dedicated Rosie to her beloved grandchildren and to the memory of Vera Sturt – Nan. “She was my saviour, the kindest, most selfless person I have ever met. How fortunate that Jo and I had her. Had I not had Nan, I would have been much more tormented. All right, I was tormented a little bit. I am not a difficult or moody person but perhaps I would have been had I not had such delicate love and kindness in my childhood. I think my books would have been unbearably cruel, given the lack of love from my father and my mother, had I not had Nan in my life. Nan saved me. She really was my angel, as I write in Rosie. All I wanted was for Nan to be my mother.”

Preparing to leave the Swiss finishing school to which Jane insisted she be sent rather than to a longed-for university, Tremain speculated about her future. “A secretarial course. Dull secretarial work, enabling the ambition of others. Men. Sex. A husband. A white gown.

“To me, it didn’t seem to be enough,” she writes. Well, said one friend, “You’ll have to wait and see, La Rose. What else can you do?” Then she repeated the hilarious exhortation of their ski instructor that they always face outward towards the void: “Tits to the valley”. It is advice that Tremain has followed throughout her life – persevering and confronting bad times head on, defusing fear with humour.

“Remember, Jackie, tits to the valley!” she urges.