Her reclusive streak was revealed on stage this morning at the Guardian Hay festival, where she confessed her ideal situation would be "to have enough money ... [to] write and not be published". She doesn't, she told Guardian Review editor Lisa Allardice, like reviews or critics. "It's a very uncomfortable thing for a writer, we're very tender," she said. Writing is the thing she does best, how she earns her money, but "not being published would be great", Atkinson continued. "When I say that to other writers they look at me as if I'm totally insane."

Even though she doesn't feel a need to be published, she said she "probably need[s] to write", a distinction which JD Salinger – who hasn't published a word since 1965, despite rumours of shelves groaning with manuscripts – would surely recognise. But it's not an "overwhelming burning urge," she added, suggesting she would "rather potter about in the garden". "My work is not my life," she said. "I started writing quite late, I didn't have that 'writing is everything, my art is all'. You have to be able to recognise the difference between the two."

Usually it takes her two years to write a book, she said, but if she were locked in a room, she could do it in the three months it took her to write her Whitbread-winning novel, Behind the Scenes at the Museum. "Probably not needing to be published would give me more time to think about a book," she said, and "without the time pressure" she could write faster.

The Whitbread’s top prize goes to one of the winners of prizes already awarded in five categories — novel, first novel, poetry, biography and children’s book. Each category winner receives $8,700, while Spurling receives the $43,000 Whitbread Book of the Year Award.

Earlier bookmakers had touted short story writer Ali Smith as the likely winner, but in the end her book — The Accidental — and Tash Aw’s Malaysian-set saga — The Harmony Silk Factory — were not in the final three as judges continued their deliberations Tuesday.

In the end, Michael Murpurgo, chairman of the judges, said that Spurling beat off strong competition from poetry winner Christopher Logue’s Cold Calls, a modern reworking of Homer’s Iliad and Kate Thompson’s children’s book, The New Policeman.

"Somehow she managed to paint a picture of a painter that was accessible to people not necessarily familiar with art. It’s an extraordinary achievement to write a book of that length, which when you get to the end you are sorry it’s finished," Murpurgo said.

Tash Aw picked up the first novel award for The Harmony Silk Factory, beating Rachel Zadok amongst others. All the category winners receive £5,000 and compete for the prestigious Whitbread Book of the Year title, which carries an additional £25,000 prize.

Honouring books from last year by writers based in the UK and Ireland, the latest Whitbread awards attracted a record 476 entries. A panel of judges - including writer Margaret Drabble, ITN journalist Alastair Stewart, actresses Joanna David and her daughter Emilia Fox - will decide the overall winner on 24 January.

Ali Smith's novel The Accidental follows a girl spending summer with a family in Norfolk. The Whitbread judges said: "From the outset, The Accidental stood out as a glorious work of fiction that inspired both laughter and sadness and that none of us could stop reading." Having been unsuccessfully nominated for last year's Man Booker Prize for Fiction, The Accidental beat Whitbread contenders Nick Hornby's A Long Way Down, Salman Rushdie's Shalimar the Clown and Christopher Wilson's The Ballad of Lee Cotton.

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Matisse The Master by Hilary Spurling won the biography award and Cold Calls by Christopher Logue took the poetry title. Kate Thompson beat three-time Whitbread winner Geraldine McCaughrean to take the children's book award for The New Policeman.