The Smallest Show on Earth (Mercury Theatre – Tour)

For a song-and-dance musical that title's a downer, and despite the entertainment it provides there are moments when the show lives up to it. In this adaptation by Paul Alexander and Thom Southerland (who also directs) of the Ealing-style film about a couple who inherit a run-down cinema, there's both too much going on and not enough.

Scenes chop and change with sound and fury, Irving Berlin standards fly by with little context and busy dancers overdo the teeth bit, if not the tits. This breathlessness leaves no room for back story; we learn little about the central pair beyond the fact that he's a failed screenwriter and she corrects his spelling. Consequently the audience has nothing to invest in their adventure, and the show, for all its fun and polish, struggles to make its mark.

Then midway through the second half something happens. Sam O'Rourke and Christina Bennington as Tom and Marlene, a likeably gauche younger couple, break out of their gawky courtship and launch into a dreamy rendition of "Steppin' Out With My Baby". Choreographed with floating bliss by Lee Proud, it's a starry moment in a show that's been crying out for one.

For the rest, Laura Pitt-Pulford and Haydn Oakley do what they can with those under-characterised main roles and battle pluckily against Ricky Butt and Philip Rham as the gleeful dastards who own a rival cinema. Liza Goddard and Brian Capron lend the encrusted cinema employees a humanity that's absent from the caricatured performances of Margaret Rutherford and Peter Sellers in the movie, and Matthew Crowe's sparky young solicitor steals his scenes like John Barrowman on speed.

Indeed, shortcomings aside, there's an unerring mood of good cheer to the evening. People of a certain (all right, my) generation will relish period touches like the twist of salt in a Smith's Crisps bag, and songs like "Blue Skies" and "What'll I Do?" are timeless masterpieces that everyone will love. But these are incidental pleasures; the glue that holds a musical together is its storyline, and here the writers stall their finale by setting up a dramatically inconsequential succession of Berlin numbers, purportedly being performed by willing locals before the main picture is projected. It's pure filler, and it gets in the way because the plot we've been watching hasn't yet wrapped.

Southerland has an impressive track record in staging shoestring fringe musicals and he brings the same economy to directing The Smallest Show on Earth. He places precision and wit ahead of spectacle; but a mid-scale stage like the Mercury needs bolder brush strokes, fewer fiddly bits of furniture and a cleaner narrative thrust if it's to dominate David Woodhead's solidly imposing set. Back in 1957 the American distributors balked at Smallest and rechristened the original fim Big Time Operators. It's not a bad motto.

The Smallest Show on Earth runs at the Mercury Theatre, Colchester, until 10 October, then tours to Coventry, High Wycombe, Glasgow, Plymouth, Crewe, Swansea and Malvern.