The grey doorway in London’s Marylebone neighbourhood here is unmarked but for 11 words spelled out across the top rail: “The greatest secrets are always hidden in the most unlikely places.”

Roald Dahl, the darkly inventive 20th-century children's author behind Charlie and the Chocolate Factory wrote that line, and it was posted above the door by his heirs, who from the small set of offices within are aggressively seeking out ways to globalise, digitise and monetise his wackily wondrous works.

The goal, as the estate prepares to celebrate the September 13th centennial of Dahl’s birth, is wildly ambitious: to have every child in the world engage with a Roald Dahl story.

To get there, the estate, with a staff overseen by the author’s 30-year-old grandson, is moving far beyond the books that made him famous: 23 television, film and stage projects are in development, as well as a Dahl-themed invention kitchen and book-inspired apps.

In partnership with the Dahl estate, McDonald's gave out selections from Dahl stories with Happy Meals in Britain; laundry detergent Persil, joined forces with the estate to urge kids to have a "messy adventure"; and Boden is introducing a Dahl-related collection of children's clothing. There's a classical music arm, too. (One result: Composer Benjamin Wallfisch wrote an orchestrated adaptation of Dirty Beasts.)

Disappointment

The estate is coming off a disappointment with The BFG, a film directed by Steven Spielberg that fizzled at the US box office this summer, although it opened strongly in Britain and there are signs of a better reception worldwide. The next high-stakes move: a Broadway transfer for a musical version of Charlie and the Chocolate Factory, which is being substantially reworked, with a new director, because the London version, despite drawing audiences, failed to wow US critics and theatre experts.

The Dahl estate’s moves come as literary estates are navigating the digital age, hoping to use technologies and storytelling platforms to persuade new generations of readers (and viewers) that a deceased author is still relevant and exciting, while being aware that overkill or poorly chosen projects could harm the works’ long-term value and reach.

Dahl is best known for five books, including, in addition to Charlie and The BFG, James and the Giant Peach, Matilda and The Witches, but there are 18 children's stories in all for which the estate is seeking to build an audience.

"With publishing shifting a lot, there is still, I think, a huge desire to bring his kind of vivid and mischievous world into other mediums," said the grandson, Luke Kelly, managing director of the Roald Dahl Literary Estate.

“We are really transferring from being a literary estate to being more of a story company, and that is a bit of a scary thing for some people,” he added. “That doesn’t mean that we’re not still going to think about the books as our guiding light. It just means that we’re also thinking: ‘How do we get these amazing words and stories into kids’ bedrooms, and into their minds and imaginations, in many ways?’”

Kelly said the estate donates at least 10 per cent of its proceeds to charity; he would not discuss revenue specifics, saying its finances are private. He said the estate has been looking for collaborators “in the highest league of their field”, with “a touch of darkness” as well as “an understanding of the Britishness of the stories”.

‘Big challenge’

Among those the estate chose in recent years: Tim Minchin, an Australian comedian and musician, who was tapped to write the score for Matilda the Musical. Minchin, a long-time Dahl fan who grew up on his books and has read them to his own children, said adapting Dahl is "a reasonably big challenge" that requires converting episodic stories into dramatic narratives and adding enough emotional punch to make them moving for adults as well as entertaining for children.

"It was very clear they understood you would ruin Dahl by making it too Disney - too sparkly or saccharine, and yet you don't want to be psychopathic about it," Minchin said. He added: "They've got the experience of knowing that if you get straight-ahead people who adapt his work, they don't necessarily capture that last elusive 10 per cent of what Dahl does that no one else can do."

The centennial of the birth, as such anniversaries do, has provided an opportunity for the estate to call fresh attention to Dahl’s work, starting with a new logo (a paper airplane fashioned from yellow legal paper, reflecting Dahl’s experience as a World War II fighter pilot and his longhand writing practices) to brand its efforts. There are multiple events in September to mark what would have been Dahl’s 100th birthday.

Cardiff, Wales, where Dahl was born (he died in 1990), is pledging a transformation into the "city of the unexpected" on the weekend of September 17th and 18th, featuring performances, readings and a pyjama picnic.

In the US, a trivia show is travelling to schools and libraries, and Dahl-themed treats are at a variety of sweets shops ("Hornets Stewed in Tar" at Flour Bakery in Boston; "James and the Giant Peach Pie" at Four & Twenty Blackbirds in Brooklyn, etc)

There are also a Twits-themed dinner ("potentially perilous pudding," anyone?) running all month in London; a new Oxford Roald Dahl Dictionary; and Love From Boy, a collection of letters from Dahl to his mother. And, away from the fray, the family is planning a private service in the author's honour.

Dahl’s books have sold more than 250 million copies. But he is not for everyone – the cruel comeuppances and the villainous adults that populate his books have been a turnoff for some parents. The estate’s offices cheekily feature, on a door, poor report cards given to Dahl by his teachers, and in the bathroom, bad reviews of his works.

"He has always been immensely popular with children, but the harder edge to his world view rubbed some people the wrong way when he first came on the scene in the 1960s and 1970s – they thought of his works as too violent, or presenting adults in too critical a light, and there was some concern that there was an anti-authority strain to his work," said Mark I West, a Dahl scholar who is the chairman of the English department at the University of North Carolina at Charlotte. But, West said, "his standing in the world of children's literature has improved over the years."

"In recent years, with the success of the Harry Potter books, there is a greater acceptance of fantasy, and a little more tolerance for the edgier works," he added.

Softer

Adaptations, particularly for stage and film, began during Dahl's lifetime. The plays were dutifully faithful to the books; the films often made the endings softer or more sentimental. For example, the 1990 film of The Witches, which Dahl denounced, altered the ending so that the boy at the story's heart could enjoy a long life as a human; in the book, he chooses a shorter life as a mouse. Dahl also professed to dislike Willy Wonka & the Chocolate Factory, the first film adaptation of Charlie. But the 1971 movie musical, which starred Gene Wilder, who died last Monday, was so popular, especially in the US, that the stage adaptation is being reworked to more closely reflect it.

In recent years, the estate has chosen more idiosyncratic, and therefore riskier, artists as collaborators – film-makers Tim Burton and Wes Anderson, for example, and playwright Enda Walsh – and has made peace with allowing changes to the plots. The two most artistically acclaimed recent adaptations – Fantastic Mr Fox, an animated film directed by Anderson, and Matilda the Musical, a stage work by Dennis Kelly and Minchin, both introduce new plot points to Dahl's stories.

Matilda, which opened at the Royal Shakespeare Company in 2010, is still running in London and is on Broadway through January 1st; there are also ongoing productions in Australia and Toronto, and a North American tour is to resume in January.

Other projects have been far less successful. A new stage adaptation of The Twits, written by Walsh and directed by John Tiffany (the team behind Once), received mixed-to-negative reviews at the Royal Court Theatre last year and has an uncertain future, even as the estate works on possible film and television adaptations.

The estate decided not to greenlight for first-class (Broadway and West End) productions an adaptation of James and the Giant Peach, with a book by Timothy Allen McDonald and music and lyrics by Benj Pasek and Justin Paul (Dear Evan Hansen). That show was staged, in collaboration with Pilobolus Dance Theatre, at Goodspeed Musicals in Connecticut and then revised for the Seattle Children's Theatre; the estate is allowing only limited licensing of their work as it pursues the possibility of a different adaptation. "The Dahl estate has reserved professional rights in case something else comes along, and that's fair," McDonald said.

On the theatrical front, next up is a new stage version of Fantastic Mr Fox, adapted by Sam Holcroft with music by Arthur Darvill, which is scheduled to have its premiere this fall at the Nuffield Theatre in Southampton, England, followed by stagings at other theatres. There are seven television shows and seven films in development, Kelly said, reflecting many of Dahl's biggest titles; among them are a film version of Matilda the Musical, and, according to a report in Deadline Hollywood, a live-action film of James and the Giant Peach, possibly directed by Sam Mendes.

Prequels or sequels to the existing books are under discussion, too, but with particular scrutiny from the estate. And the estate has high hopes of breathing new life into less well-known titles. Last year, Judi Dench and Dustin Hoffman starred in a popular British television adaptation of Esio Trot; the Weinstein Co acquired the US rights.

With Charlie and the Chocolate Factory, on the other hand, the estate has a top-selling title but must figure out how to satisfy those who love the novel; those who remember fondly the 1971 film or the 2005 Johnny Depp remake; and those who know none of the above.

The stage musical, directed by Mendes, opened in London in 2013 to mixed reviews; the US production will be directed by Jack O'Brien, who is promising changes, and it will feature a new and more avant-garde collaborator: puppeteer Basil Twist.

David Greig, the Scottish playwright chosen to write the book for the Charlie musical, said each adaptation is a moment for the estate to shape how Dahl lives on. "Instead of just saying yes to people's offers," he said, "they start saying: 'What do we want? What is the legacy we want?'"

New York Times