I first saw Showstoppers! The Improvised Musical as part of the 2009 Edinburgh Fringe Festival and have wanted to watch them again ever since. I got the chance to tonight when, with the help of the audience, they created Whatsonstage.com - The Musical.

At the start of the show the audience voted on the plot for the new musical. The chosen plot set the musical at the Prince of Wales Theatre on the night of the prestigious Whatsonstage.com Awards. Quite astonishingly, the winner of the Best Actress in a musical award has not yet been chosen, despite the imminent start of the award ceremony.

The leading candidate is then found dead in her dressing room and all hell breaks loose. What follows is a hilarious show, containing more plot twists than Deathtrap and Legally Blonde put together. In addition to choosing the plot, the audience also got to name a few musical theatre composers to inspire the music of the show. And so the styles of Sondheim (naturally), Kander and Ebb, Cole Porter, Kurt Weill and Rent were all included in the score – and very successfully so.

The Rent-inspired closing number – drawing on that greatest of all theatre principles – "the show must go on" was a particular favourite of mine, the cast managing to grasp the somewhat hyped and self indulgent tone of Rent, in a tribute, rather than a mocking way. This was, essentially, a musical about musicals. And I ask you – what can possibly be better than that?

As for the cast, they are all fantastic performers and more than keep up with the MC, who continually throws curve-balls their way. There were a few sticky moments where the actors talked over each other or tripped over their words, but that just comes as proof that the show is entirely improvised. Most of the time they bounced off each other, and the audience, to great effect and picked up each other’s cues perfectly.

The best thing about Showstoppers! The Improvised Musical is that you can go see it every night of the week and it will be a completely different show every time. They are on at the King’s Head until the 21 December 2010 and I would strongly recommend catching them before they close.

You get to witness a brand new musical, which you help write and direct, come to life before your eyes. The result will, without a doubt, be one of the funniest nights you will even spend in a theatre. As for Whatsonstage.com - The Musical – look out for it. I have a feeling it’s going to be Theatreland’s next big hit.

- Ronny Lavie