Eighteen years ago, Rod Hunt, a father over-anxious about his young son’s reading, had a revelation. It was to have a profound effect on his own life and that of millions of children. His son was struggling to read, making slow progress through a structured look-and-say scheme with one-word-a-day flash cards. It was a frustrating business. But during one session the boy was attracted to a page in a book that showed a barn on fire. “He read that page with such ease,” says Hunt, “that I realised if he was motivated enough he would read.”

A deputy head in a middle school in Oxford at the time, Hunt began to consider writing his own scheme and embarked on research based on classroom observation. He wanted to write attractive, bite-sized, funny stories with a simple text and strong, matching visual narrative, using a step-by-step, word-by-word, page-by-page approach. The rest, you might say, is history.

Two-hundred-and-thirty bite-sized stories later, the Magic Key series, Rod Hunt’s much loved tales about Biff, Chip, Kipper, Floppy the dog and their friends, are the mainstay of the Oxford Reading Tree. Launched in 1986 and now the UK’s most popular reading programme, the scheme is used in three out of four primary schools, its books read by more than 3 million children a year world-wide. Its success has been enhanced by the way Hunt’s formula has tied in so neatly with the national literacy strategy. It must also have something to do with the fact that, even now, each story is tested in the classroom before publication.

Not bad for a teacher with two small children and a mid-life crisis who packed in the day job to dedicate himself to a risky venture. It’s a risk that has paid off spectacularly, however. Hunt describes the early years - when he and his family lived on advances from his publisher-in-waiting, Oxford University Press - as “nailbiting”, but acknowledges that over the past six or seven years he has started to make “big money”. He says he is “comfortable”, but not a millionaire.

That could soon change. For Hunt’s characters are about to become television stars. The independent production company, HIT Entertainment, spotted the small-screen potential of the Magic Key stories and the result, after delicate negotiations with the BBC and Oxford University Press, is a series of 26 programmes to be shown on BBC Schools and BBC Children’s television from Monday.

With the TV programmes will come the inevitable flood of related merchandise. Schools will be able to buy teaching packs, and, through an exclusive deal with Marks and Spencer, from October parents will be able to buy Magic Key story books, videos, dot-to-dot and number books, comics and pyjamas. Biff, Chip and Kipper could become the latest commodity craze for four to seven-year-olds, a unique phenomenon in the history of school reading schemes.

Any parent who has supported a child through the Oxford Reading Tree will know how successfully the books capture the attention and affection of early readers. They will also know how much the Magic Key stories are a spur to reading fluency. Children are often determined to make their way through the earliest stages of the scheme as quickly as they can, eager to enter the world of the Magic Key that older pupils enjoy and talk about.

The magic key is discovered by Biff in an old dolls’ house tucked away in a hidden attic after the family moves house. Whenever the key glows the children are transported into a parallel world of fantasy adventures. “The key is really a metaphor for unlocking the imagination,” says Hunt.

The stories have a timeless appeal, supported by the illustrations of Alex Brychta - Hunt’s creative partner from the start. Though the illustrations literally represent the text, so children can follow the stories in words and pictures, they are full of hidden jokes about everyday life, many rich in an irony that adults can appreciate. As a parent who has been through the Reading Tree three times, I have never tired of Brychta’s visual cracks about the school caretaker and the nosy neighbour, to name but two of his inspired minor characters.There is something in the books for all of us, children, teachers and parents.

Brychta and Hunt are as sought-after for school visits as any other successful author or illustrator. They have become VIPs, called upon to open schools, and receiving dozens of letters a week from children with their own ideas for new Magic Key adventures.

Even though Hunt and Brychta have been hoping for years to see their characters on television, they are nevertheless nervous about the HIT initiative. A project that has been so close to them and that they have controlled and tailored for so long has been taken out of their hands. The programmes and tie-in publications are quite different, being wholly new material with stories written by a team of scriptwriters overseen by Jocelyn Stevenson, who has previously been involved in writing and creating award-winning programmes such as Sesame Street and The Magic School Bus.

They have been animated by Collingwood O’Hare Entertainment, which has produced more than 150 animated children’s series for television, including Dennis and Gnasher and Oscar’s Orchestra. Some of the characters’ traits, such as Biff’s bossiness, Kipper’s mischievousness and Wilma’s common sense, have been expanded for the programmes.

HIT initially intended to make mainstream children’s entertainment programmes out of the Magic Key stories. But then it opted for a two-pronged approach, to entertain and to educate by delivering literacy-hour objectives using a new range of stories. Each of the 26 programmes is 15 minutes long and contains a two-minute introduction on the theme and key objectives; a “Floppy” moment full of doggy activities and humour to reinforce the objectives; a seven-minute Magic Key adventure (which will also be broadcast separately on Children’s BBC); a one-minute reinforcement of the objective and a 30 second “wrap-up” of the theme at the end.

For example, in “HMS Sweet Tooth” the learning objective is full stops, a theme that is tied neatly and imaginatively into the adventure without forcing the point. The programmes are professional, well constructed, bright and breezy, although they lack some of the precision and ironic sparkle of Brychta’s illustrations. HIT, however, has no doubt they will be a success.

HIT’s chief executive, Peter Orton, says: “What you will see is a wonderful extension of the Reading Tree. We have tried to capture as much as we can of the original concept, while creating something new. Never before has this quality of animation been put into an educational programme.”

Although Brychta has requested that the illustrations in the tie-in books be sharpened up for the next batch of publications, he is happy with what he has seen of the programmes so far. “I think they will enhance the Reading Tree rather than detract from it,” he says. “There is a limit to how much I can interfere. At some point you have to let go.”

Perhaps one of the strengths of the Reading Tree is that it has been built up slowly, taking small but undoubtedly lucrative steps along the way, responding closely to the needs of schools. Television is a different beast and can create an explosion of interest that is capable of fizzling out just as quickly. Brenda Stones, publishing director of the education division of OUP, acknowledges that television can create “extremes” but is confident that the Reading Tree will continue to develop. She says: “I am confident people will fall back on the original books. The core stories will go on and on even if this new bubble bursts.”

The Magic Key series will be broadcast on BBC2‘s schools’ slot from Monday, September 25 at 9.30am and on Children’s BBC television from Friday, October 13 at 3.45pm.