LONDON — British actor Ian McKellen has revealed the first picture of himself playing a 93-year-old Sherlock Holmes in a new movie.

Filming has begun on “Mr. Holmes,” which imagines the famous sleuth in his old age as a retiree living in seclusion by the sea. The movie, based on Mitch Cullin’s novel “A Slight Trick of the Mind,” sees the detective struggling with a failing memory and revisiting one final unresolved mystery.

The 75-year-old McKellen tweeted a picture of himself in costume as Holmes this week, saying: “Over 70 actors have previously played Sherlock Holmes. Now he’s 93 years old and it’s my turn.”

Laura Linney, his co-star, plays Holmes’ housekeeper.

The film, directed by Bill Condon, is due for release next year.