"If you had the chance to relive your life, what would you change?" That question, posed in bold letters outside the Shaftesbury Theatre, has taxed the minds of philosophers and artists down the ages. But the only thing taxed by this blandly competent, psychologically conservative American musical is one's patience.
It started life as a 1986 Francis Ford Coppola movie. Now the original authors, Arlene Sarner and Jerry Leichtling, have enlisted Bob Gaudio to add 22 songs, while preserving the basic structure - that of a hindsight saga in which the soon-to-be-divorced Peggy Sue is whisked back in time to 1960, where she becomes a 17-year-old high-school student armed with the mind and memory of a 42-year-old woman.
This offers scope for endless jokes about her pre-knowledge of everything from the Kennedy presidency to the rise of the microchip. But the really big question is whether she will turn up at the prom and marry her chauvinistic beau Charlie, or whether she will abscond to Paris and study to become a cook.
You only have to invoke Sondheim's not dissimilar Merrily We Roll Along to see what the show lacks: dramatic irony and historical perspective. By starting in 1980 and working backwards, Sondheim's musical poignantly shows the loss of both individual and social idealism in postwar America.
But the very thing that Sondheim laments, this musical actively celebrates. It argues that Peggy Sue, having had a random fling with a motorcycling beatnik, would be better off settling down to suburban life with a faithless husband than pursuing the path of self- fulfilment. Its assumption that the status quo is infin-itely preferable to radical change is a dismal conclusion.
Gaudio's songs show technical proficiency but are let down by Leichtling's lyrics, which lapse into the usual sogginess at moments of passion. On the positive side, Ruthie Henshall as Peggy Sue combines a Doris Day girl-next-door charm with a hint of sexy Dionysian wildness.
There is good support from Gavin Lee as a nerdy scientific genius - why on earth didn't she marry him? - and from Melanie Marcus as a mischief-making redhead. Ruari Murchison's camera-shutter sets and Kelly Robinson's production also exhibit commendable efficiency. But the musical is meant to be a dynamic form.
This one, with its stand-by-your-man ethos, feels like a hymn to emotional stasis.
· Booking until next March. Box office: 0870 906 3798 .