Ian McKellen Has Clapped Back at Critics. Now He’s Playing One.

In Anand Tucker’s new film “The Critic,” Ian McKellen plays Jimmy Erskine, a closeted reviewer in 1930s Britain who covers theater with equal measures of wit and acid. “Despite her crimes against the theater, she was sensationally gorgeous when drunk,” Jimmy writes of a young actress portrayed by Gemma Arterton.

Naturally, McKellen luxuriates in such lines. When the screenwriter Patrick Marber (“Notes on a Scandal,” “Closer”) sent the actor the script, he said, “‘This is the best part I’ve ever written for anybody,’” McKellen recalled. “Well, I didn’t want to appear to be rude by not doing it.”

At 85, the actor is not slowing down, and continues to test himself by playing unlikely roles (just four years ago he was a rather mature Hamlet in London) and collaborating with directors like Robert Icke. Only a recent accident temporarily set the actor off course: In June he fell off the stage during a fight scene in “Player Kings,” Icke’s adaptation of Shakespeare’s “Henry IV” diptych, in which McKellen played John Falstaff.

“The Critic,” which comes to theaters Friday, was shot over five weeks. “The budget was very small for what we were trying to achieve, Ian was 83, it was really hard,” Tucker, the film’s director, said. “But he was just on it — and he’s in almost everything.”

This could also describe McKellen’s decades-spanning career: He has been in almost every kind of production — fantasy blockbusters like the “Lord of the Rings” films, onstage in plays by Shakespeare and Beckett and in drag as the dame in the beloved British holiday tradition known as pantomime.