Actor David Tennant will not be returning to play Hamlet "before Christmas" because of a back injury, the Royal Shakespeare Company says.
The 37-year-old, who is scheduled to have an operation for a slipped disc on Thursday, said his enforced absence was "hugely disappointing".
His understudy Edward Bennett, who received standing ovations on Monday and Tuesday, will continue to stand in.
Tennant's run as Hamlet at the Novello Theatre is due to finish on 10 January.
He played Hamlet 60 times in Stratford-upon-Avon in the summer ahead of the production's London transfer.
"My back problem has progressed to the point where it is currently impossible for me to carry on without surgery," Tennant said in a statement.
"I want to get back onstage as quickly as possible and I am very grateful to Ed who has courageously got to grips with the role but in a much shorter time. It's a fantastic achievement."
Artistic Director Michael Boyd said: "We all wish David a speedy recovery and it is an indication of the RSC's investment in understudies that Ed Bennett can take over Shakespeare's largest role at such short notice."
The RSC said refunds would not be issued "because the company has a fully rehearsed understudy policy".
"The company is able to offer exchanges, subject to availability, for other RSC London performances during this season at the Novello Theatre," it added in a statement.
Bennett, who normally plays the role of Laertes, received mixed reviews after Tuesday's press night performance.
Edward Bennet had been originally cast as Laertes
The Guardian's Michael Billington said the actor's Hamlet was a "more robustly traditional reading of the part which marks Bennett down as an actor to watch".
But Charles Spencer from the Telegraph said: "For sheer nerve and self-confidence, Bennett undoubtedly deserved the cheers. It has to be said, however, that he is not a natural Hamlet."
Tickets for the London shows sold out within three hours when they went on sale in September.