By Aleks Phillips, BBC News
Sir Ian McKellen has been taken to hospital after falling off stage during a performance of Player Kings at the Noël Coward theatre in London.
The 85-year-old actor was in a fight scene when he lost his footing and fell. It is not clear whether he has sustained any injuries.
The audience was evacuated from the theatre and informed that the evening show was cancelled.
Player Kings is a production of Henry IV, Parts One and Two, and started its 12-week West End run in April.
Sir Ian – who plays John Falstaff – was circling a battle scene involving the Prince of Wales and Henry Percy, when he fell off the front of the stage. As the house lights came up, the actor cried out and staff rushed to help.
One member of the audience told the BBC the incident was “very shocking”.
“I really hope that he is going to be alright,” Sandro Trapani said.
“As far as I saw, he was conscious because he was asking for assistance.”
Sir Ian’s previous Shakespeare credits include roles as Richard II, Coriolanus, Iago, Richard III, King Lear and Macbeth. He is also set to star as Hamlet, in a new film adaptation directed by Sean Mathias.
His on-screen credits include Gandalf in the in The Lord of the Rings and The Hobbit trilogies, and Magneto in the X-Men movies, as well as roles in Beauty and the Beast, The Da Vinci Code and Mr Holmes.
The actor also appeared in 10 episodes of the ITV soap Coronation Street as the scheming romance author Mel Hutchwright.
Five years ago, Sir Ian was forced to cancel a King Lear showing at London’s Duke of York theatre after sustaining a leg injury while running to catch a train, but ensured the audience was in for a good time, by sitting on stage and answering questions.