Edinburgh on Thames

Showstopper! The Improvised Musical offers a brand new song-and-dance spectacular at every performance. It opens with a brilliantly chaotic piece of comedy. A theatre producer on stage telephones Cameron Mackintosh and pitches him a new musical. Mackintosh answers and the producer invites ideas from the audience. ‘What’s the setting?’ Someone yelled ‘Late-night sauna’ at the performance I saw. The producer, without missing a beat, told Mackintosh that the show would be called, Sweat, Sweat, Sweat. If that was improvised it was world-class. The show develops along the lines suggested by the crowd and a number of hit musicals are parodied.

The audience, I suspect, enjoyed this more than me. The character of the producer faded away and his improvisational panache was forfeited. The sets and the costumes on stage appear rather drab and perfunctory because they have to be adaptable to any number of cues from the audience. The visual palette is dominated by red and black and the show looks as if it hasn’t quite left the rehearsal room. And though the performers sing superbly, they lack glamour and stardust. Showstopper! comes to the West End in October and its backers are hoping to recruit a fan base of addicts who will come back again and again. It may work. But I wouldn’t bet my last penny on it.

The Christians by Lucas Hnath looks at fundamentalism in America’s Bible belt. The show consists entirely of speeches given at the altar of a new church founded by the powerful and charismatic Pastor Paul. He boasts that he built up his congregation from nothing and turned the church into a wealthy and popular seat of worship. Having paid off his debts, he announces a new teaching.