The Shawshank Redemption, Wyndham's

A beloved if flawed film becomes the latest celluloid icon to stumble on its way to the stage, The Shawshank Redemption on the West End flailing where theatre adaptations of The Graduate, When Harry Met Sally, and Rain Man, among various others, previously led.

Devotees of the 1994 Oscar hopeful may bring enough prior affection for the material to see them through the (copious) chinks in the prison cell armour, leaving newcomers to this parable of liberation pondering how it is that a piece so devoted to inspirational uplift should seem so uninspired.

Co-authors Dave Johns and Owen O'Neill scored a success with their play earlier this year in Dublin, a city not as used to the presence of visiting thesps on the order of Kevin Anderson and Reg E. Cathey as is London, which trades theatre people back and forth with New York all the time. The two guest Americans do perfectly well by roles essayed more eloquently in the movie by Tim Robbins and Morgan Freeman, not least because a long film (well over two hours) affords their symbiotic journey more quality time. Shawshank's problem in this rendering has to do with a story busy parading before us its hymn to life's possibilities without bringing much either interesting or new to the table. This is drama by numbers, and not just those pinned to the prison garb of the all-male ensemble.

You'll no doubt already have a whiff of the story: in 1940s Maine, a literary-minded banker by the name of Andy Dufresne finds himself (wrongly, he protests throughout) serving a double life sentence for the murder of his wife and her lover. While doing time in the state's toughest penitentiary, the emotionally cautious, reticent Andy finds a friend in an older con, Red, a resident fixer far better at keeping his fellow prisoners supplied with cigarettes than at convincing those in charge that he might be worthy of parole. A Rita Hayworth poster is one request  from Andy to Red that comes in handy, though the play stops sadly short of the defining Raquel Welch image giving the movie's last reel its share of va-va-voom.

The film is a peculiar if undeniably affecting amalgam of brutality and greeting card bromides, the latter writ large in a playtext that posts some of the more prominent homilies on the front of house. (Thankfully, "Some birds aren't meant to be caged, their feathers are too bright" is too long for easy duplication atop Charing Cross Road.)

The creative team behind the play, Irish director Peter Sheridan included, have made much of this absolutely not being the movie transposed to the stage and of the greater importance of Stephen King's source novel to the enterprise at hand. In fact, what one gets is a mixture of identifiable reprises from the film - an early scene of sexual abuse visited upon Andy is very nearly identical - and notable departures: I far preferred the OTT fate meted out to Bob Gunton's fearsomely bespectacled warden in the movie to the path travelled by any of the cartoonishly acted prison officials in a theatre production whose dodgy American accents - the two leads self-evidently excepted - are perhaps inevitable given this show's provenance.

There's considerably more made on stage of Andy's  bookishness: so much so that one wonders if this apparent numbers whiz of a moneyman might not actually be an English prof at some prison-themed fancy dress party. (Meanwhile, the dual references to Lolita complete the cross-referencing begun a week ago by the incarcerated state in which we find Brian Cox's Humbert Humbert at the National.)

But the unfortunate truth is that the play doesn't really  dramatise events when it can skip glibly over them, the entire sequence in the movie of Red's re-emergence into society - among the film's best passages - here done away with in favour of direct address to the audience that allows Cathey's gravelly-voiced Red to get straight to the heartwarming nub of the evening.

Marking his fourth London stage appearance, onetime Steppenwolf actor Anderson looks a lot like Robbins, but his comparably baby-faced Andy is far more genial and lacking in guile than the distant, enigmatic figure we find on screen. Whereas the film dabbled in Mozart, the play gives us a band, with Geoffrey Hutchings along for the ride as the hapless librarian played in the movie by James Whitmore: neither one gets beyond the cardboard conception of the character as kindly. And doomed.

Shawshank itself will surely strike a chord with audiences ready to buy the t-shirt reaffirming the overriding paean to hope: an Obama-era mantra that may make this live presentation timely in a way that the film, a commercial flop upon its initial release, was not a decade-and-a-half ago. But it will take considerable goodwill to forgive dramaturgy that more or less collapses in the final section, once Red and Andy hurtle toward a destiny that - spoiler ahead! - exists to be shared.

Many will recall the importance to this story of a particular rural location to which Andy summons Red in one of the more urgent stretches of the film. That same sequence on stage is marked by the sudden noise of a barn animal to alert us that we're not in Kansas - sorry, Maine's meanest prison - anymore. Up until that point, I had thought the fight director was the most vital offstage participant in a testosterone-filled if fundamentally inert production. Nope. With a single "moo", the sound designer wins that accolade hands down.

• The Shawshank Redemption is at Wyndham's Theatre, London, until February 14, 2010. Book tickets or go to www.theshawshankredemption.co.uk