Showstopper!, Leicester Square Theatre, London

Little Briton with a large talent

Matt Lucas is partly responsible for some of the most visceral and grotesque humour in British comedy. So it was both intriguing and refreshing to see him in an altogether more ponderous, and sometimes bashful mood, for his guest role in this improvised musical.

Sporting a dark velveteen suit with what looked like a 1960s-style red Arsenal shirt underneath, Lucas (a known Gunners fan) was vaguely in line with the black and red costumes of the cast. Though he was all dressed up and ready for action, the Little Britain star was principally employed as sidekick to writer/director Dylan Emery, whose charisma and passing resemblance to Rowan Atkinson are both noteworthy.

The show's scenario is that Emery has just one night to create a new musical. What follows vacillates between the ensemble doing his and Lucas's bidding as they up the improv ante.

Suggestions from the audience are also used to create the musical "From Dust 'til Dawn", a tale of love, celibacy and betrayal through the eyes of the employees of a Mexican oyster bar, which journeys through a range of musical stylings, from Andrew Lloyd Webber and the Disney composer Alan Menken, to Sesame Street.

When the cast settle on the dust theme of the musical as relating to cocaine smuggling, Emery asks the characters to think of five euphemisms for the drug. "Venezuelan Tate & Lyle" one of them comes back. Meanwhile, wearing an impish smile, Lucas names two characters Hannah and Steve but dryly requests that the former be a man and the latter a woman, adding supportively: "it's just like Cyd Charisse and Gene Kelly."

Lucas's suggestion morphs into a so-so number about the differences between being a boy and a girl. It's a tune that would not look that out of place in Avenue Q and, while there are better songs, for example a Disney-style duet called "Two Birds", Showstopper! does approach a product that, as co-creator Adam Meggido (playing the hero Pedro tonight) has said, "could sit alongside anything in the West End." Fortunately for the cast, this achievement says more about their talents than it does about the formulaic and trite musicals going on around them.

Meanwhile, just as it was starting to look like Lucas would never be able to demonstrate his own performance dexterity, Emery casts him as Pedro's Yorkshireman brother, thus providing a late twist in the tale. Visibly reluctant, Lucas assumes his role as Balthazar Jones, here to inform Pedro that his real name is Barry and that he should come back home to his mum.

Lucas is asked to sing for his supper too, but it's a short refrain. Nonetheless, his presence during this enjoyable romp has provided both entertainment and a unique snapshot of the depth and duality of his comic persona.

To 30 July ( www.showstopperthemusical.com )