While everyone this side of Inverness (and possibly that side as well) knows the words to The Proclaimers' three hit songs, it still takes large kahunas to create a musical on their enduring strength. Yet in the same fashion as Mama Mia!, though without the universal appeal or back catalogue, their music was fashioned into a stage show with moderate success, and now a film. That's how it is when you're on your way from misery to happiness (uh huh).

I'm Gonna Be (500 Miles) is the show stopper, but it's Letter From America which forms the narrative arc that starts when best pals Davy (George MacKay - The Boys Are Back) and Ally (Kevin Guthrie) leave the army and return home to Leith, Scotland. Ally resumes his romance with Davy's sister Liz (Freya Mavor) while Davy starts one with her colleague Yvonne (Antonia Thomas). As love blossoms, Davy's mum and dad (Peter Cullan - War Horse and Jane Horrocks - Little Voice) are about to celebrate their 25th wedding anniversary. It's all big smiles and sunshine until Dad receives a letter from the past: worlds jolt and lives unravel.

There's an awkwardness about Sunshine On Leith that sophomore director Dexter Fletcher (Wild Bill) never really overcomes. Mostly it's a problem of tone as his characters remain relentlessly cheery until they're pitched into a desperate sadness from which they emerge relentlessly cheery once more. This might work on stage but feels hopelessly contrived in a world that aims for a 'gritty, dirt-under-the-fingernails experience'. It's far from that. The weakness is compounded by leaden staging and choreography which come the grand finale has the panache of a high school flash mob.

On balance, Fletcher achieves a certain amount of feel-good helped by toe-tapping songs and an attractive cast who engage in an absurd amount of hugging and back-slapping. But with too many excursions across the cringe line, and without the convincing emotional grit that sets apart musicals like Billy Elliot, it's unlikely that you'd go an extra 500 miles for Sunshine on Leith.

// COLIN FRASER

Previewed at Sony Theaterette, Sydney, on 26 March 2014