The world’s most famous statue? The image of Michelangelo’s David is certainly known throughout the globe, and it was only a matter of time before writer Mary Hoffman tackled it in her work.

“It was a bit like a mountaineer knowing that they would have to scale Everest,” she said. “You can’t be interested in Renaissance art and not be interested in David. I always knew that one day I would write about him.”

She fell in love with Italy at the age of 20, when she took an art history course in Florence as part of her English degree. “I have been going back ever since, as often as I can,” she said. And you can’t go to Florence without being deluged by pictures of David.

“It’s everywhere in Florence. It is really debased — you see it on tea towels, mugs, all this tourist tat. I was interested in getting back to how people saw it at the time. It is very high – 17ft tall. It’s known as the giant.

“We are used to it now, but what must it have been to see this thing for the first time? I was trying to imagine a world in which the statue doesn’t exist.”

She had plenty of scope to turn this into fiction. “We know about the block of marble. We have a copy of the contract and the date. But we don’t know anything at all about the model or even if there was one. You have a framework, and in the centre is this hole where you can put your invented character. The only clue is that the muscle of the right arm looks like a stonecutter’s arm.”

In her book David, the model is Gabriele, a stonecutter from Settignano who travels to Florence in search of his ‘milk-brother’, the sculptor Michelangelo. She has woven Gabriele’s story into the known facts: the debate about where the statue should go; how it was trundled to the Loggia in a sling; and the reaction of the crowd . “The story arose out of the proposition: what would happen to a young man who came to Florence at that time looking like that, but with clothes on. He was so gorgeous that everyone wanted a piece of him – men and women.”

She made her name as a children’s writer. Her first book was published in 1975 as White Magic. Since then, she has written 95 books for children and teenagers, including the award-winning Amazing Grace, a picture book about a little black girl which former US president George Bush’s wife Laura claimed as her all-time favourite. More recently, she has produced the Stravaganza series about a group of Islington teenagers who have the gift of “stravagating” or time-travelling to a violent fantasy version of Italy called Talia. David is her third historical novel — the others being The Falconer’s Knot (set in 13th-century France) and Troubadour (14th-century Italy).

She works in the study of her home in a converted barn in Carterton, where she moved ten years ago from London. In Haringey she had been at the centre of a campaign to protect libraries, and last year found herself involved in the Oxfordshire protests, particularly the battle to keep Bampton library. She comes from a modest background — her father was a railwayman — and believes that without libraries she would never have found her way to Cambridge or to a career as a writer. An enthusiast of new technology — she communicates with her young fans via Twitter and Facebook and is publicising David with a ‘blog tour’ — she is worried about how future generations of writers will earn a living, particularly her daughter, Rhiannon Lassiter, author of two series of young adult novels, who works at Oxford Brookes University. The pair linked up in a 2003 anthology of war writing in aid of Unicef, to mark the invasion of Iraq.

The cover of David warns that it is not suitable for younger readers, and there is certainly plenty of sex and violence. “I hope adults will read it as well as older teenagers. There is plenty of action. It was a dangerous time to go into the street — you could easily be mugged and stabbed.” David’s Florence is in the grip of gang warfare, where followers of the Medicis and Savonarola clash in street battles and young Gabriele’s sexual encounters earn him dangerous enemies.

At 66, she is now busy on her next book. “I’m going to be found dead at the laptop,” she said. This one is for adults — a “contemporary romantic comedy with a darker underbelly”. Hoffman books definitely have a dark underbelly. David should certainly make readers look at Renaissance Florence with fresh eyes.

* David is published by Bloomsbury at £10.99.