By Victoria Lindrea
BBC News entertainment reporter
Last month saw the inauguration of a new Tony Award which recognises the best performance given by an actor or actress who takes over a leading role in a long-running show.
Simon Russell Beale takes over in Spamalot in December
It is a tricky proposition for any actor, especially where a prior performer has been acclaimed by the critics or the role has been filled by a high profile star - as Henry Goodman found to his cost.
British actor Goodman replaced Nathan Lane in the original Broadway production of The Producers in March 2002, but was sacked after just four weeks in the role.
Producers of the New York show claimed Goodman lacked the necessary chemisty to play Max Bialystock, saying he was "the right actor in the wrong role".
"It wasn't because I went out there nightly and couldn't do it," Goodman told the BBC in 2002. "I have affirmation that my performance was enjoyed, and thrillingly so."
Melanie Griffith gave a star turn in Chicago on Broadway
Nonetheless the actor was abruptly replaced, despite a nine-month contract with the show.
To be eligible for the new Tony award, which will be handed out for the first time next June, performers must be contracted to star in a role for at least six months.
Such a policy should neatly cirmcumvent celebrity stints in shows like Chicago.
Where star casting is designed to boost ticket sales and flagging celebrity, management set much greater store by long-term replacement casting.
In December, Simon Russell Beale steps into Tim Curry's shoes as King Arthur in the sell-out Broadway musical Spamalot.
Russell Beale is an acknowledged star of the stage and three-time winner of the Olivier Award for best actor - and must surely be in the running for next year's Tonys.
It's an indication, as Guardian theatre critic Michael Billington suggests that "the stigma has been taken out of re-casting".
"It used to be the case that you opened with a mega-star and then the casting got less starry as you went on," says Mr Billington.
"Nowadays that's totally untrue - quite often you find the person taking over is just as prestigious as the person who created the role in the first place," he says.
Sinclair plays the role created by Gene Wilder in the 1968 film
"Actors are no longer loath to take over from someone else."
"These days what happens is an actor often goes in and recreates the role in his own terms - he doesn't offer a carbon-copy performance, but rethinks the role."
John Gordon Sinclair, who took over from Lee Evans in the London production of The Producers, made no secret of the fact that he wanted the role of Leopold Bloom from the outset.
"At that time they knew they wanted Lee Evans to do it, so I was just waiting for him to leave," he told the BBC in April.
Nigel Harman, who takes over from Ewan McGregor in the West End production of Guys & Dolls this Christmas, faces different challenges.
Although a well-known face on British television, the 32-year-old EastEnders star does not carry the celebrity kudos of McGregor - and producers will have to rely on a strong performance from Harman to bring in passing tourists.
McGregor drew the crowds but not the critics' plaudits
However, with a background in musical theatre, Harman's performance may prove more critically successful than his Hollywood predecessor.
"What this is all about ultimately is the long-running show," explains Mr Billington. "No actor likes to be tied up forever in a show."
"Management must ensure that the third cast or the fifth cast is as good as the original, and not simply a shadowy replacement."
And Harman can take heart from Mr Billington's recollection of Alex Clunes, who replaced Rex Harrison as Professor Higgins in the original My Fair Lady.
"The show hadn't lost anything - in fact it had gained. Clunes was a better actor and a better Professor Higgins."