The West End transfer of the Menier Chocolate Factory's production of Merrily We Roll Along is a cause for celebration. Maria Friedman's production of Stephen Sondheim and George Furth's 1981 musical (which the creators adapted from George S. Kaufman and Moss Hart's 1934 play) won rave reviews – not to mention the Critics Circle prize for Best Musical – when it opened at the enterprising Southwark venue last year, and now fits quite snugly into the Harold Pinter Theatre. While it's inevitable that the show has lost some of the close-up intimacy that it must have had in the smaller space, its warmth and wit still resonate in its new home. Expertly orchestrated by Friedman (in a distinctive directorial debut) and buoyed by the great work of a crack cast, the production soars, even if its confidence can't entirely obscure some of the flaws in the show's design or the ultimate conventionality of its perspective.   

The show's history is famously chequered. A big flop upon its Broadway debut in 1981, when the performers took to wearing sweatshirts bearing their characters' names in order to help out those bemused by the reverse-chronology structure, Merrily was subsequently redrafted by Sondheim and Furth, and its quality reappraised thanks to two well-regarded British productions: Paul Kerryson's 1992 version at Leicester Haymarket (in which Friedman starred) and Michael Grandage's Olivier-winning Donmar production in 2000.

The main challenge of the piece is, of course, its time scheme. The show opens in 1976, at a Hollywood party that goes spectacularly off the rails, and ends in 1957, with a sighting of Sputnik on a New York rooftop. In the interim, it rolls back the years to trace the trajectories of a central trio, composer Frank Shepard, his writing partner Charley Kringas and their writer chum Mary Flynn, as they variously sell out, break up, bond and collaborate, moving from present-day acrimony back to past camaraderie. As Mary struggles to repeat the success of her first book, and Charley loses Frank to the lure of Hollywood, the piece adds up to an(other) elegy for America's loss of innocence and the fading of the Dream, presented through a comfortably cynical take on showbiz success – one that allows Sondheim and Furth to reflect, in a highly self-conscious manner, upon their own art form.

What does the reverse-chronology structure add to all this, beyond clever-clogs gimmickry? There's doubtless a touch of the latter to the show's design, but Sondheim and Furth (following Kaufman and Hart's lead) have been rather strategic in their construction of the piece. Told straight, the show's corruption-by-success narrative might look obvious and bluntly moralising. Told backwards, it still does, a bit, but there are clear gains to the structure, as the audience involve themselves in piecing together the arc of the characters, from where they end up to where they started out. "How did you get here?" ask the chorus, repeatedly, of Frank, and the refrain sounds equal parts sympathetic inquiry and accusation.

Added by a sharp and sleek design by Soutra Gilmour, Friedman keeps the action tight and sparky with swift, staccato transitions between scenes and musical numbers, giving the evening an edgy energy that's quite invigorating. There are some genuinely great songs – the opening "That Frank" and the closing "Our Time" are among the highlights – and Tim Jackson's choreography brings witty life to the wonderful party interludes, with the cast moving brilliantly together to form a mincing menagerie of  hangers-on and sycophants.   

The leads are a joy, too. As the gifted composer whose betrayal of friends, lovers and self takes him to the top of the showbiz ladder at a painful price, Mark Umbers demonstrates once more his irresistible charisma. Jenna Russell is raspy-voiced perfection as she shows Mary's unfulfilled ambitions and unrequited love turning her into a caustic sot. And Damien Humbley is winning as Charles, his frustration at Frank revealed in a show-stopping rendition of "Franklin Shepard, Inc." Clinging to one another during a gorgeous "Old Friends", the three generate a magical warmth. And, while all of the cast are strong, special mention must go to the supremely stylish Josefina Gabrielle, who's simply delicious as Frank's self-consciously seductive second wife, a character whom Sondheim and Furth (rather uncharitably, it must be said) point the finger of blame at for tempting our hero off his principled path and down the road of commercialism.        

For a show that's been tinkered with so much – Michael Grandage has commented that it has many more versions than Hamlet has Quartos –  the structure of Merrily is quite sound. Still, some of the stitching does show through and Friedman's production isn't able to fully disguise this. There's a definite mid-show slump; a bogus scene set at a courthouse surges into sentiment and features two below-par pre-interval numbers: the drippy "Not A Day Goes By" and the underwhelming "Now You Know". Though often praised for the complexity of his characterisation, Sondheim also notably resorts to some crude portrayals here, such as the depiction of two Southern characters as dumb-hick racists who despise NYC. There's also a certain expediency to aspects of the plotting: it's a tad too cosy that the character who doesn't take the commercial route gets rewarded for his integrity with a Pulitzer-worthy Broadway success, while the contrast between "selling out" (ie. going to Hollywood to make movies) and "keeping it real" (staying in New York to work in theatre) that the piece develops is not as complexly worked out as it might be.

A graced, genuinely moving final scene mitigates these shortcomings, though, and finds Furth and Sondheim at their best. Richly entertaining, full of zing and zest, Friedman's production finally does full justice to the show's unmerry undertow, and the poignancy of its chararcters' interwoven journeys from experience to innocence.    

Merrily We Roll Along, at Harold Pinter TheatreAlex Ramon reviews Merrily We Roll Along At the Harold Pinter Theatre4