A small Greek island, its wooded hills woven with timeless secrets, would make a welcome contrast to the carnage of first world war trenches. But if 1917 director Sir Sam Mendes now has a holiday isle near Athens in his sights, it is as the location of his next project, and not as a sunny destination before he is feted at Bafta and Oscar ceremonies next month.

Mendes and his partners at Neal Street Productions are to make a major television adaptation of The Magus, the mysterious and much-loved novel by John Fowles. “Like many people, I read and loved it as a teenager,” Mendes said this weekend, as he unveiled his latest plans to the Observer.

The director believes the twisting, layered plot of the 1965 bestseller will be suited to television. Fowles wrote the book, which was made into a film in 1968, after teaching English at a school on Spetses, and it tells the story of the enigmatic and reclusive resident of an island villa who controls the lives of those who come into his orbit. “There are lots of modern classics like this one which were compressed into movies in the past and perhaps lost something by squeezing them, instead of telling them over several hours,” said Mendes.

“There’s a whole raft of good books that fall into that category and now we are in a position where we can tell it differently.”

Inside the Covent Garden offices Mendes shares with three partner producers, there is no question of taking a rest after the run of hits they have enjoyed. Between them, Mendes, Nick Brown, Caro Newling and Dame Pippa Harris are also responsible for staging Stefano Massini’s acclaimed theatrical event, The Lehman Trilogy. And 1917, which this weekend has reached a box office figure of almost £22m in just a fortnight, received its clutch of Oscar nominations in the same week that their BBC One television show Call the Midwife racked up top viewing figures of seven million and their outlandish Jez Butterworth-scripted show Britannia announced a third season on Sky. Now, in addition to developing The Magus, the Neal Street quartet is to bring a musical version of the cherished 1983 film Local Hero to the Old Vic theatre this summer. The partners are also making a comic thriller series for television set in London’s financial markets. Called Prophets and written by Krysty Wilson-Cairns, the acclaimed 32-year-old Scot who co-wrote 1917 with Mendes, it deals with the shady and high-stakes business of predictive investing.

Facebook Twitter Pinterest Spetses. off the Aegean coast, is the setting for John Fowles’s 1965 novel. Photograph: Robert Harding/Alamy

“It is a world that really exists, but is quite hidden,” said Brown. “There’s a lot of money to be made working out where tornadoes are going to hit next and the likelihood of an earthquake, or even which CEO is likeliest to drop dead.” Wilson-Cairns, a mathematician, was inspired by memories of time she spent as an intern in an actuarial company – before being thrown out for asking innocently if they would be warning the potential victims of an upcoming disaster. “Our series will focus on predicting individual deaths, rather than disasters,” explained Brown.

“There’s so much private health information out there now and it is not such a big step for someone in a firm like that to think ‘actually, I really need this person to die now’.”

Wilson-Cairns honed her darkly humorous idea in her trailer during the making of 1917, said Harris: “Krysty is a very witty writer, and the hit TV shows Killing Eve and Succession have proved you do not always need to have likeable protagonists.”

Mendes did not draw on his co-writer’s full comedic powers for 1917, he admitted, adding that he now sees Wilson-Cairns as a test case for the company’s handling of an emerging talent. “She shows how cross-pollination from TV to film can really work.”

Among other talents working in the loose Neal Street stable are Butterworth, John Logan, who wrote Mendes’s first Bond film, Skyfall, and the playwright David Greig, who is working on the new Local Hero musical alongside Dire Straits’s Mark Knopfler and the film’s original director, Bill Forsyth. “We had a short run in Edinburgh and it was good that we did it there first, because they would have been most critical of any faults in Scotland, where the film is regarded as a national treasure,” said Newling, the theatrical impresario of the team.

“Mark has written 19 new songs for the show and has become quite an intuitive theatre animal. He wants to revisit some of his music for London.”

Mendes has frequently stepped between stage and film work, but said he still thinks of theatre as home. “I felt like theatre would always be there for me, but I’ve never felt that way about film,” he said. “After all, there are some great film-makers who have sometimes struggled to get something made. So I have been relieved in many ways, as well as pleased, by the great reception for 1917. It’s been a decade since I made a movie that was not part of a franchise – and even back then Revolutionary Road was based on a well-known book.”

He and Harris originally looked into making The Magus several years ago, but gave up when it appeared too legally complex. But while making the Bond films they met Ian Fleming’s great-nephew, Robert Lacock, who had the rights to Fowles’s book. They have since developed the project with him, bringing in screenwriter Tom Edge, best known for the film Judy and the BBC One detective series Strike.

Mendes regards himself as “a pretty benevolent hands-off kind of producer”.

He aims to be closely involved at the beginning of both new television projects, he said, before stepping back to let them “police themselves”.

“In terms of helping to get the first stages of these shows right, I am really eager to see Prophets through, and The Magus too, although it is more Pippa’s project.”

Further off, Neal Street is looking at the possibility of making a feature-film version of Call the Midwife, the TV show that gave the company financial stability, and of The Lehman Trilogy.

If there is one secret behind these successes, Mendes suspects it is the shared rule of only making scripted drama that they all care about. “We have had moments when we wondered what we were doing, but we stuck to our plan,” he said. “At least one of us has to be totally committed to a project. There is no cynicism about any of the choices we make.”