Ian McKellen has tweeted the first photograph of himself starring as a nonagenarian Sherlock Holmes in the Bill Condon mystery Mr Holmes.

The new film, which will hit cinemas next year, centres on an aged Holmes who becomes obsessed with one final case. It is based not on Sir Arthur Conan Doyle's original 19th century stories about the famous English sleuth, but the 2005 novel A Slight Trick of the Mind by Mitch Cullin.

Tweeted McKellen, 75: "Over 70 actors have previously played Sherlock Holmes. Now he's 93 years old and it's my turn."

A Slight Trick of the Mind features Holmes as an elderly man unable to walk without a cane and with a failing memory. He lives with a housekeeper and her son, and makes an effort to talk with the son about his life before he forgets it entirely. Laura Linney will co-star in the film version, for which principal photography began last week on location in the United Kingdom.

Condon is the Oscar-winning screenwriter of Gods and Monsters, which he also directed, and the Golden Globe-winning director of period musical Dreamgirls. He also wrote the screenplay for the Oscar-winning musical Chicago and directed sex drama Kinsey. Condon's most recent film is last year's Julian Assange biopic The Fifth Estate.