When the credits rolled at the end of the third and supposedly final film in the Wachowski brothers' science fiction trilogy, most people assumed they had seen the last of The Matrix. Not so, according to star Keanu Reeves, who reportedly told a London audience that a fourth and fifth film may be in the works.

US site Aintitcool.com says Reeves broke the news while speaking at the London School of Performing Arts to promote his new film, Henry's Crime. The site's correspondent writes: "He met the Wachowskis for lunch over Christmas and stated that they had completed work on a two-picture script treatment that would see him return to the world of the Matrix as Neo.

"[He] says the brothers have met with Jim Cameron to discuss the pros and cons of 3D and are looking to deliver something which has never been seen again. Keanu stated that he still has an obligation to the fans to deliver a movie worthy of the title 'The Matrix' and he swears this time that the treatment will truly revolutionise the action genre like the first movie. [The] Wachowskis are working on a movie called Cloud Atlas at the moment, once that concludes they will talk again."

The news comes as a surprise for two reasons: firstly, the final Matrix film, The Matrix Revolutions, rounded off the story arc fairly precisely, with the machines and humans having secured peace. Secondly, the final two films in the series are widely considered to have been failures, with Revolutions coming in for particular criticism. The films still managed to pull in more than $1bn at the global box office when combined, however.

Since completing the series in 2003, the Wachowskis have directed only one film, anime-inspired flop Speed Racer. They have plans to bring a modern-day take on the legend of Robin Hood to the big screen. Cloud Atlas will be an adaptation of the 2004 David Mitchell novel, a series of six interlinked stories set in a variety of different eras, from the 19th century to the far future.