EXCLUSIVE: Downton Abbey star Hugh Bonneville has signed to play the lead in Dead Simple, a feature version of the bestselling crime novel.

Peter James, the British thriller writer, is developing Dead Simple, the first novel in his bestselling crime series, as a feature. Swiss TV scriptwriter Daniel Eckhart is adapting the screenplay.

James has partnered with producer James Simpson and entertainment lawyer Leighton Lloyd of Los Angeles-based law firm Gipson Hoffman & Pancione to develop the project. Simpson and Lloyd will be in Berlin talking to prospective sales companies.

James is one of the UK’s bestselling crime writers, whose books have sold more than 10m copies to date worldwide translated into 34 languages. His latest book in the series outsold both James Patterson and Jeffrey Deaver in the UK, pipping Deaver’s James Bond novel to number one on the Sunday Times Best-seller list.

ITV Studios was planning to adapt his Roy Grace books for television but James took the rights back as the development process stretched on too long. BBC Scotland also made noises about adapting the crime series for TV after the books were optioned by Company Pictures (Skins).

Director Roman Polanski has also circled Dead Simple, a race-against-time thriller about a bridegroom buried alive after a stag night prank goes wrong. Bonneville’s character, Brighton-based detective Roy Grace, must find this living coffin while coping with the mysterious disappearance of his wife.

Bonneville said: “I instinctively feel that my strengths as an actor chime with the principal qualities found in Roy Grace and I’m tremendously excited at the prospect of bringing him off the page and onto the screen.”

A hedge fund and other private investors are lined up to put money into Dead Simple. James is bullish about making pre-sales to France and Germany given his popularity as an author in both countries. “We’re pretty confident that we can get a chunk of the budget out of France and Germany given its popularity in these territories. It’s quite a big brand in both countries. My sales in Germany equal those of the UK,” said James.

James was a film financier before reinventing himself as a crime author seven years ago. He co-founded the Movision film partnership in the 1990s, which financed 13 features with a combined budget of $300m. Titles that James executive produced include Guy X, starring Natascha McElhone, and The Merchant of Venice, starring Al Pacino.

James said: “I just thought I would go back to my roots and make Dead Simple as a major movie. Most authors don’t have that kind of film finance background. I thought I might make a better job of it myself by taking control of my own destiny.”

As to why his Roy Grace books, which, on the face of it, would seem perfect for TV given the success of other detectives such as Inspector Morse or Sherlock, have not made the transition to the small screen, James said his novels are thrillers first and foremost. “The reason the books have been successful is that they get away from the typical plodding police procedural, that Agatha Christie kind of thing where you start with the body in the library,” said James. “My books are thrillers although they have police procedure in them. British television just didn’t seem to get it.”

Three of James’ other novels have already been adapted for television. US network ABC produced Host as a TV movie back in 1998 and Five adapted The Alchemists in 1999 while ITV filmed Prophecy in 1995.

Not Dead Yet, the eighth book in the Roy Grace series, will be published on June 7.