Lauren Child is the face and brains behind some of Britain’s best-loved children's books, Charlie and Lola and Clarice Bean. But now there’s a new girl in town — Ruby Redfort, a super smart agent and code-cracker, who looks set for similar global supremacy.

Ruby’s creator will be in Oxford tomorrow for the final of a nationwide children’s code-cracking competition, and is then fitting in a book-signing session at Waterstone’s.

Lauren said: “My new character Ruby Redfort may be a super-smart agent and code-cracker, but is also a 13-year-old girl. So when I wrote Ruby Redfort, my publishers and I wanted to come up with an idea which schools might like to get involved with and we thought that it would be fun to find the best code creators out there.”

She will be joined by mathematician Marcus du Sautoy, of Oxford University, who devised the code for the book.

Competition aside, Lauren, 46, relishes any opportunity to meet her readers, saying it’s crucial to her work.

“I absolutely love both meeting children at events, particularly the older readers of Clarice and Ruby, and getting letters from readers. It is wonderful to hear their feedback and it often gives me ideas for stories.

“I get lots of letters and emails from readers too, and I try and write back. They often tell me about the funny and moving things about their lives.”

So where did Lauren’s inspiration for Ruby Redfort come from?

“It was really from the American films and TV series that I loved as a child,” Lauren said. “There were the Nancy Drew mysteries and the films of Jodie Foster and Tatum O’Neal such as Freaky Friday and Paper Moon, but also TV detective series such as Hart to Hart, which I loved.

“For other books, and illustration, a lot comes from artists that I love — Matisse, Braque, and from film and other illustrators that I admire such as Angela Barrett and her work from Snow White and Princess and the Pea, Ronald Searle's Molesworth or St Trinians illustrations, Pippi Longstocking orginal artwork, US illustrator Maira Calman’s Max in Hollywood and Sara Fanelli’s myths and legends book — I love anything from that.”

Lauren won the Kate Greenaway Award in 2000 for I Will Not Ever Never Eat a Tomato, the first of her Charlie and Lola picture books. Her third Clarice Bean novel, Clarice Bean, Don’t Look Now has sold over 500,000 copies. Then in October 2005, the BBC launched a 52-part animated series of Charlie and Lola which has won three Baftas and aired in more than 34 countries.

It was only through sheer perseverance and pig-headedness that she managed to publish anything at all. Having hawked her wares around London’s publishing houses, she settled into a series of temporary jobs, painting for Damian Hirst, designing chandeliers and decorating china.

No one wanted Clarice Bean until Lauren wrote a book called I Want A Pet, which was published, and then everything else was bought, too.

So does she still remember the despondency of those lost years?

“It does feel weird sometimes, because I did struggle for so long to find a publisher before Clarice Bean: That’s Me was published in 1989. But I also knew I didn’t want to compromise and I think I must have felt instinctively that it was worth waiting, because I didn’t really start out planning to be a writer and illustrator — it was more by accident than design. So my advice would be to try and come up with your own unique style and voice, and just keep trying. It takes a huge amount of determination.”

Lauren’s determination has obviously paid off. But does the advent of Ruby mean the end of Charlie and Lola?

“I published Slightly Invisible last year, the fourth Charlie and Lola picture book,” she said. “But at the moment there are no plans for more Charlie and Lola picture books, although I have written lots of new stories which would be wonderful to illustrate at some point in the future. We are planning some board books of the original picture books and box sets for slightly younger readers.

“But I don’t really write or illustrate with a particular audience in mind. I suppose it’s something to do with remembering what it felt like to be a child.”

Lauren Child will be at Waterstone's at 4.30pm tomorrow.