Tomorrow Morning, Landor Theatre, London

(Tim Parker)

The title of Laurence Mark Wythe's musical (first seen at the New End in Hampstead in 2006) will serve as a wish for new musical theatre in Britain. According to Stephen Sondheim's lyric in West Side Story. "Something's coming, something good, if I can wait."

Meanwhile, interestingly mediocre sub-Sondheim shows like this are the staple fare of endless workshops, showcases and other development processes. George Stiles and Anthony Drewe (with Honk!, Just So and new songs for Mary Poppins) are the closest we have to rivals to Andrew Lloyd Webber.

Wythe, however, is a bit more than promising. He writes music and lyrics with a sure touch and a consideration for singers, who repay the compliment at the Landor in Clapham North. Delightful Julie Atherton, eager Jon Lee (formerly of S Club 7), moody Yvette Robinson and handsome Grant Neal are first-rate. But why are they miked in so tiny a venue?

Wythe's show – directed to the max by Robert McWhir, with a smart design by Chris de Wilde – is really only a song cycle for two couples, one on the brink of marriage, one about to divorce. It dawned on me that they may be the same couple, separated by 10 years. There is no real fire but there are one or two hot spots: a tango of secret addictions that nearly works; a lyrical duet for loving dads ("Look What We Made"); a narcissistic torch song ("Girl in the Mirror") touchingly discharged by Atherton; a good opening number.

There is one funny line: "Just because he had sex with his patients doesn't mean he wasn't a good vet." But there is something hopelessly dated in the telephone call and message items and no compensating sense of period or detail in the lyric as there is, say, in Lloyd Webber and Don Black's Tell Me on a Sunday.

To 13 November (020 7737 7276; www.landortheatre.co.uk)