Showstopper! The Improvised Musical has been a hit at the Edinburgh Fringe for nearly 10 years but, for the first time, it will play a full-length run at a West End theatre, having been partly crowdfunded.
More than 600 performances across the world and several short stints in London theatres begs the question: Why has the show - which sees the cast make up an on-the-spot musical based on audience suggestions - taken so long to get a coveted West End run?
"The West End is a totally different ball game, the Fringe is amazing and is huge every year," explains cast member Ruth Bratt.
"To have grown from a tiny 70-seater Portakabin in what is essentially a car park most of the time - it's taken a long time to grow the show.
"The idea for Showstopper! - which is improvised - is that it should be as good as a West End musical, so we've always had aspirations to be in the West End but it takes a long time to raise the money and get the backing to get here."
And so, for the first time, the company has turned to crowdfunding site Indiegogo to raise money towards putting on the three-month run.
Donations were rewarded with perks including personal performances and songs to front row seats.
But Bratt says it's about more than simply raising money.
"You are also raising awareness of what you are doing and building excitement plus it was a good way for us to reward people who have watched the show for years.
"People come back time and time again to see the show in Edinburgh so we do have a lovely loyal support group and it was nice to be able to give something back so that they would definitely get seats."
In a notoriously competitive, often overcrowded market which has left the West End littered with failed shows such as Stephen Ward, I Can't Sing and Dr Zhivago, even an established Fringe and touring audience doesn't guarantee success.
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"What we have noticed is that the audience is slightly different in the West End because there are a lot of tourists here. But there are people who just love coming to West End shows, so hopefully there is a new audience there, too.
"It's very much a gamble, any West End run is, and we just hope the word gets out."
With more than 600 performances, Bratt says she is confident that the company has never, knowingly or otherwise, repeated any songs or themes with the show being different every night, based on the suggestions thrown at them.
"The bit of your brain that you use to memorise isn't the same part of your brain that you use to improvise, it's quite difficult to do. Sometimes people will say, 'Oh I saw you do a show about this', and you have no recollection of it at all.
"You do worry about repeating yourself but even if you do a love story one night and again the next night, the story will be completely different and the characters will be completely different so its actually quite hard to repeat things," Bratt explains.
However some people remain unconvinced that the show is improvised, she admits.
"There's nothing you can say, in a way it's quite flattering. There are times when you say, 'Really? You thought that story wasn't improvised. When it's about dinosaurs?'
"No-one would have written that, you would be laughed out of town."
Showstopper! The Improvised Musical runs at the Apollo Theatre Shaftesbury Avenue until 29 November.
