Merrily We Roll Along, Menier Chocolate Factory, London, review If ever a show illustrated the truth that musicals aren't so much written as rewritten it is Stephen Sondheim's Merrily We Roll Along. The show opened - after febrile last minute revisions during previews - on Broadway in 1981. In Sondheim's pained words both the critics and the theatrical community were "merciless" and the show closed after just 16 performances. But Sondheim is not an artist to give up without a fight. He and his writing collaborator George Furth continued to tinker with the piece and Sondheim finally felt they had got it right with a UK production in unglamorous Leicester in 1992. Maria Friedman, one of our greatest musical theatre actresses, starred in that show, and now, 20 years on, she is making her professional debut as a director with Merrily We Roll Along. It's a superbly assured production from a woman who really understands what makes Sondheim tick. She sharply captures the show's wit but also discovers its undertow of sadness and loss. Like Harold Pinter's Betrayal (1978) this is a work that moves backwards in time. The early scenes, showing the main characters in compromised middle age, are set in the Seventies. Gradually, scene by scene, we go back in time, finally arriving in 1957, when the three first meet and became devoted friends, full of exuberant hope for the future. "We're the movers and we're the shapers," they sing, "We're the names in tomorrow's papers." After witnessing all the damage that time, dodgy decisions and bad faith have inflicted on them, this cheery song seems the saddest number in the show. If the musical has a fault it is that it sometimes seems a little too neat and schematic, in a way that Pinter's Betrayal with its ache of love and remembrance never does. Sondheim doesn't dig as deep. But as a piece of craftsmanship Merrily We Roll Along dazzles, from the opening acidly depicted Hollywood party, when the characters" dreams and friendship have curdled, to the poignant hope of their first meeting. The score ranges from the touchingly emotional to the brilliantly comic, often with a jazzy swing to the music that hints at something much darker beneath. And Soutra Gilmour's sleek designs neatly capture changing times and fashions. Mark Umbers has the trickiest task as the main character Franklin Shepard, a composer turned Hollywood hotshot who betrays his friends, his wives and his ideals in the course of the show. Sondheim never satisfactorily explains why he sells out so easily, or quite succeeds in making this shallow opportunistic character dramatically interesting, but Umbers plays him with such charm and swagger that you can see why his friends stay so loyal for so long. Jenna Russell is deeply touching as the woman who holds a hopeless torch for him, turning alcoholic to numb her pain, and Damian Humbley gives a deliciously geeky performance as the lyricist who in one of the show's most entertaining songs turns devastatingly on his writing partner during a live TV interview. Watching this assured and original show more than 30 years after its ill-fated premiere it's clear that far from being a flop, Merrily We Roll Along is actually one of Sondheim's most startling and affecting achievements. 020 7378 1713; until Feb 23; www.menierchocolatefactory.com