Ian McKellen staged an impromptu Q&A session with theatre fans on Saturday (04Aug18) after he was unable to perform in West End play King Lear due to an injury.

The Lord of the Rings star was on his way to the Duke of York's Theatre in London to perform in a matinee of the William Shakespeare play when he suffered a leg injury while trying to catch a subway train. As a result, he was unable to perform in the physically-demanding show, and decided to make it up to theatregoers by staging a surprise chat with them instead.

"I hadn't long been up before I set off for yesterday's matinee of King Lear. At the underground station I galloped up 45 steps to catch the train above. Once on it, I skipped along the carriage and my left leg gave way," the veteran actor explained in a note on Twitter.

"A strained calf muscle was diagnosed and was painfully pummelled back into life," he continued. "Instead I chatted on stage to the audience while they waited for their money back and I tried out a few new routines and some old ones - a bit of (Lord of the Rings character) Gandalf and a couple of Shakespeare speeches."

He explained that he was well enough to sit down and chat with the audience, but he wouldn't have been able to kneel during a rainstorm scene, or carry the corpse of Cordelia on his back during the show.

The 79-year-old returned to perform that evening, with the help of a walking stick, and finished his note by assuring fans that he will be back to normal when the play resumes on Tuesday.

"I just want to reassure those who have tickets for Tuesday, our next performance, that I'll be back again, muscle restored and spirits high. And repeated apologies to Saturday's audience who missed Lear and got just me instead," he wrote.

King Lear runs until November.