Barry Cunningham knows a thing or two about what makes a good children's book.

Back in the mid-1990s while working as a children's editor for Bloomsbury, Barry was sent a manuscript from literary agent Christopher Little. The tale of a boy wizard by first-time author JK Rowling had already been rejected by countless other publishers, but all were left red faced and counting the cost of their decision, when Harry Potter and the Philosopher's Stone hit bookshops in 1997, spawning a phenomenon the likes of which had never been seen.

"People think writing children's literature is easy, but it's not," says Barry, who learnt his trade touring round the country with the likes of Roald Dahl.

"You have to believe what you are doing, you almost have to become the child you're writing for.

"What I liked instantly about Harry Potter was the sense of magic, the promise of things to come, but also I loved how the children gave each other courage, they were a tight-knit group that you really wanted to be a part of."

While the Harry Potter bandwagon was still at full pelt, Barry left Bloomsbury and in 2000 founded Chicken House, a dedicated publisher of children's literature. Discovering authors who have a talent for storytelling and a voice as distinctive as Rowling's, can be, he admits, like finding the proverbial needle in the haystack, but with the hope of luring new writers out of the woodwork he recently launched a children's fiction competition in The Times newspaper. The winner was Reavers' Ransom by Harrogate author Emily Diamond.

"Emily's novel has everything," says Barry.

"It's got a great storyline, really believable characters and the writing has a real sense of style about it. Sometimes you look at novels by first-time authors and you think, it's great, but that's probably the only book they've got in them.

"With Emily it's different, I really believe we've discovered not just a great book, but a great writer."

Set in the 22nd-century in an England partially flooded by climate change, Reavers' Ransom follows the exploits of Lilly Melkun who finds herself embroiled in the kidnap of the Prime Minister's daughter.

As a lifelong environmentalist and more recently a Friends of the Earth campaigner, Emily admits the subject matter came easily, but was wary of beating her readers over the head with a very large stick.

"When I was growing up I read the Susan Cooper series over and over again," says the 37-year-old.

"Those "Stories had a huge impact on me and my one ambition when I started to write was to ensure the story was something readers could relate to. I've got a background in global warming and from that I came up with the idea for a girl sailing a boat through London.

"I quickly learnt that it's one thing having an initial idea and another turning it into a coherent 300 pages.

"I got halfway through that first book and realised I didn't know where it was going.

"When I finally went back to the drawing board, I had a much greater sense of what the story was, but even then it still took a leap of imagination to think I would ever finish it.

"The one thing I did know was that it couldn't be preachy. It may have an environmental message, but ultimately readers want to be entertained."

Having entered the book into the Chicken House competition, Emily admits she went into self-denial about her prospects of being short-listed and believed that if she even thought about winning for a moment, it wouldn't happen.

However, three months after posting off her manuscript she received a call from Barry which changed everything.

"Knowing I'd made it to the final was amazing, finding out I'd won was almost surreal," she admits. "Suddenly you see all your months of late nights transformed from a pile of A4 paper into an actual proper book. I know I've been incredibly lucky."

With Reavers' Ransom just out, Emily is already working on a follow-up and with Barry's support she has every chance of making it on to the bestsellers list.

"When I first met Emily, I instantly saw the connection between her and the character of Lilly," he says.

"For me that connection between a writer and their characters is crucial if a book is going to be a success and spark a reader's imagination.

"After Harry Potter, publishers were inundated with copycat fantasies, but now I think we have come out the other side and there is much more emphasis on realism and the tough side of growing up.

"Of course, there's still a certain amount of snobbery in the literary world about children's writing. I'm not sure that will ever change, but when you find a special writer like Emily, it makes the job worthwhile."

Reavers' Ransom by Emily Diamond, published by Chicken House, priced £6.99.