Children's writer Julie Hearn knows her eyesight is deteriorating. At some point in the future, her congenital condition will prevent her from spending too long poring over old texts in the Bodleian Library, where she researches the period detail for her popular historic novels.

This worrying development does not discourage her, she tells me at her cosy Victorian terraced home in Abingdon, because her storytelling vision is becoming clearer with every book she writes.

"I'm a glass half-full person, so I try not to let things upset me," said Julie, who is in her forties.

"Once my right eye goes I will not be able to read but I will go into the Bodleian with my magnifying glass, and if it takes an hour to read a whole page, I will still do it, because no-one else would hone in on the same kind of tiny details that I do."

It was thorough research and attention to detail that won Julie critical acclaim for her debut Follow Me Down (2003), a timeslip story, and The Merrybegot (2005), which focused on witchcraft. Now her third novel, Ivy, is being published. For each novel, she is doing less research, and letting her imagination do the work for her instead.

"As a former journalist, I was very focused on getting the facts right, but now I am using facts more as background. I have started my next novel, Hazel, and I don't know how it is going to end my imagination is working much harder," she said.

Ivy tells the story of a young girl destitute in Victorian London, who falls in with a crowd of thieves, and it only takes a few passages of lively Dickensian dialogue to transport the reader back in time.

The thieves spirit wealthy children away from their nannies to strip them of their clothes, so they can be sold in the markets of Petticoat Lane.

The thieves don't think twice about turning a girl into a laudanum addict to keep her quiet. Years later, Ivy finds her way back to her family, but before she can settle into a drug-fuelled stupor, she is spotted by a wealthy painter who asks her to be his muse.

Ivy's family order her to sit for him and then the past returns with a vengeance.

Julie once cleaned for a lady who had a copy of the Rossetti painting Beata Beatrix, and then read the story of Lizzie Siddal, Rossetti's wife and model, who died of an overdose of laudanum.

"It made me think of writing the story of a girl who was very poor, and who was discovered by an artist. Then she gets involved in a bohemian art world and knows she has to get out.

'Ivy gets addicted to laudanum, which I think gives the book a contemporary edge, because young girls do find themselves in all sorts of situations.

"The drug is my device for keeping her passive throughout the novel, and this makes the ending more meaningful when she finally takes control of her life."

Ivy is the first part of a trilogy that Oxford University Press has commissioned Julie to write. The next book, Hazel, will focus on Ivy's daughter, who is a teenager at the time of the Suffragette movement.

"I wanted to write a big family saga, and the book after Hazel will be about a young lad during the Blitz," Julie explained. "Ivy will be in her nineties and I will be able to show how events early in her life affect the course of family history."

Since becoming a writer, single mum Julie, whose daughter is now studying for A-levels, has met other writers in Oxfordshire, but says she is not keen on organised events, because she is quite a solitary person.

"I bumped into a fellow writer in Oxfam the other day, and she said 'I have finished it!' and I knew just how relieved she felt. I don't know why we were in Oxfam, because we are both getting good advances!"

Now in the middle of writing her fourth book, she can't imagine anything else she would rather being doing.

Julie said: "I like working on my own. I know some people would find it difficult, but it really suits me. I have so many characters roaming round in my head that it feels like there is a crowd of people in the room. Sometimes the characters in my head are more real than the people who come through the door, and I need a reality check.

"Simple tasks like a trip to Tesco at lunchtime can be quite difficult if you have been stuck in another century."

Julie might not be one for socialising, but she is looking forward to the publishers' launch of her new book at London's top restaurant, The Ivy if she can drag herself away from her latest work in progress.

"It's a good job I didn't call the book McDonald," she joked.

Ivy is published by Oxford University Press at £5.99.