Heartache of a real sensation

Helen Oyeyemi's parents still haven't read the novel that will make their 19-year-old daughter a literary star. They didn't even know she was writing it until she told them she had signed a two-book deal with Bloomsbury for a reported £400,000 advance (exaggerated, says Helen, who will not disclose the exact amount).

How could she write a novel without them finding out, especially since she did it on the computer in their bedroom? "I told them I was doing homework. They thought I was writing a really long essay," she says, laughing. "When I signed the contract I thought I'd better tell them. They thought I was joking. But then again, they had been getting reports from school saying, 'Helen's homework is never in on time.' They couldn't understand it."

Why doesn't she want them to read it? "Because the book is about Nigeria, and they are first-generation Nigerians. I came over here when I was four years old. Jess, the main character, feels she is on the outside wherever she is. In England, she doesn't feel she's English; in Nigeria, she doesn't feel she's Nigerian. It's like that for me but I don't know how much a first-generation Nigerian would connect with that. I can't do any of the things my mum can do - such as cook Yoruba food - and when I have kids, all that is probably going to die out. For her to read my book, it would be like watching her culture die."

So, for now at least, her parents are banned from reading it. When their daughter finally allows them to, she says, "That will be the verdict that matters."

Helen's novel, The Icarus Girl, focuses on eight-year-old Jessamy, who, while on a visit to relatives in Nigeria, meets Tilly Tilly, a ghost only she can see.

There, the book gets darker - Tilly Tilly wants Jessamy's body for her own.

It started as a short story Helen wrote in January last year. Seeking advice on how to develop her writing style, she emailed it to Robin Wade, a literary agent, whose name she found in a directory. Instead of sending her away with a few tips, he said he wanted to represent her. Helen told him she had written 150 pages. "In fact," she says with a mischievous glint in her eye, "I'd only written four. I begged my English teacher to give me time off homework so I could write it."

By May, when she should have been revising for her English, sociology and theology A-levels, she spent all her time writing. Wade showed the story to Alexandra Pringle, editor-in-chief of Bloomsbury, who was impressed: "The prose sings immediately right from the first page," she said.

"I signed the contract on the day I got my exam results," says Helen. It is a testament to her ability that she could write an extraordinary debut novel in six months, get three As with minimal revision, and be accepted at Cambridge, where she is now in her first year, reading social and political sciences at Corpus Christi College.

Her strong imagination, she says, developed as a result of being kept indoors for most of her childhood. On arriving in England, Helen's parents moved to a council estate in Lewisham, where they still live today. "My mum didn't want me to hang around the estate, so I grew up doing lots of reading, writing and watching television. I never saw friends outside school. I had an imaginary friend called Chimmy and all sorts of other imaginary things going on."

Her parents, who had both been teachers in Nigeria, had to retrain when they moved here, her father working nights as a security guard to put food on the table. He is now a teacher for children with special needs, while her mother is training to be a Tube driver. There was never much money and with three children - Helen has a sister, Mary, 15, and a brother, Tony, six - sharing a rented two-bedroom flat, it was lucky that they are all extremely close. This was compounded by the discovery when he was four years old that Tony is profoundly autistic. "We had seen it coming. He was behaving oddly; for instance, his tantrums were unusually bad, and he wouldn't look directly at you, always side on."

Tony is now at a local special school, but still needs lots of care and attention. "We try to make things easier for each other. My parents both work so we all share looking after Tony. Mary must be looking after him more now I'm away at university." She pauses. Does she feel guilty for leaving her younger sister to cope? "Yes, but I think Mary is more maternal than I am. Playing with him is quite a strange experience. You can't touch him unless he wants you to. He will come to you if he wants to be touched; I have to sit there and see if he wants to play."

Helen started writing when she was seven, changing the endings to books such as Little Women if she wasn't happy with the way they finished. Her stories then were very girlish, but by the time she was 12 or 13, they had taken a much darker turn. Her teenage years were marred by deep depression. "I had a really hard time at secondary school," she says of her comprehensive, Notre Dame in Southwark. "I felt I didn't fit in. I wrote lots of angsty stories that make me cringe now." She laughs, but her depression was not the usual teenage angst. She had very few friends. "Nobody liked me. Depressed people are difficult to get along with because they're so self-absorbed. I cried during lessons and at lunchtimes. I didn't speak to anyone. There was one time when I remember I didn't speak at all for a month. Because I wasn't communicating with anyone, I had to write things down. I think my writing really developed around that time. I would stay off school 'sick' a lot and read." Her favourite authors were Sylvia Plath and Emily Dickinson. "It was good in terms of literature," she jokes, making light of a bleak time.