Robert Hardy will no longer play Sir Winston Churchill opposite Helen Mirren as the Queen in upcoming theatrical production The Audience.
The actor, 87, recently suffered a fall and cracked some ribs yet continued to perform in previews of the production at the Gielgud Theatre last week.
Producers said last night that Hardy has decided that a schedule of eight performances a week over a long run "is not sustainable".
He has therefore "reluctantly" stood down.
The part of Churchill will now be played by Bafta-winning actor Edward Fox who has agreed to stand in at very short notice.
The director Stephen Daldry said: “Robert is one of theatre’s great actors and for him to have accepted this challenge at his age speaks of his courage and commitment to the theatre."
"That he feels unable to continue is a great sadness to us all but we respect his decision and wish him a return to full health and strength very soon.”
The Audience will continue to play at the Gielgud with Hardy’s understudy, David Peart, playing his role until Fox takes over.
Daldry said he was "incredibly fortunate that at very short notice Edward Fox has kindly agreed to step in."
Adding: "We are particularly lucky to find an actor of such stature and great authority to play Winston Churchill and we are delighted to welcome Edward to the Company.”
Fox is famous for his portrayal of Edward VIII in TV drama Edward and Mrs Simpson. He won a Best Supporting Actor Bafta in Joseph Losey’s The Go Between and was “The Jackal” in Day of the Jackal directed by Fred Zinnemann.
Joining Mirren and Fox in the star-studded world premiere of Peter Morgan’s play are Michael Elwyn as Anthony Eden, Haydn Gwynne as Margaret Thatcher, Richard McCabe as Harold Wilson, Nathaniel Parker as Gordon Brown, Paul Ritter as John Major and Rufus Wright as David Cameron.