Betty Blue Eyes, Novello Theatre

Foot fetishists will have a field day at Betty Blue Eyes, given that the producer Cameron Mackintosh's latest venture is also the first in my experience to sing of bunions, calluses and corns, the last encompassing a passing reference to a lyric from Oklahoma!: another show on Sir Cameron's CV.

But the happy news is that musical enthusiasts will themselves find reason to cheer a defiantly homegrown entry that turns a comparatively little-known film (A Private Function) into a generous-hearted, eminently tuneful tribute to British decency and pluck. The duck à l'orange may within the context of the piece turn out to be so much marmalade-smothered spam, but Betty Blue Eyes is the equivalent of a proper Sunday roast - pork, of course, not beef.

Indeed, some may wish for rather fewer trimmings as the second act piles on helpings to befit the sort of properly conceived book musical one rarely encounters anymore; that, in turn, makes Betty at once endearingly old fashioned and these days almost radical in its marriage of a sustained narrative to an entirely original score. It may, in fact, be the creators' understandable excitement at the musical profligacy on view that the knife with which the porcine Betty is threatened hasn't been taken to the work as a whole. When you've got this much imagination and heart, where do you begin to slice?

Not in the first act, that's for sure. From the jazzy, up-tempo overture (and a post-interval entr'acte to match), it's clear that the songwriting team of George Stiles (music) and Anthony Drewe (lyrics) have at last hit the commercial big time that has oddly been denied the Olivier Award-winning duo during their 28 years as collaborators. Never previously have they reached the mainstem with a show to call their own - until now. (Their contribution to Mary Poppins was as an add-on, essentially, to the Sherman Brothers' venerable film score.)

The source material may seem unlikely: after all, how far can you go with the emphasis on flatulence and the inevitable verbal gamesmanship ("agog" rhymes with "hog") to be derived from the 1984 Alan Bennett/Malcolm Mowbray/Maggie Smith film about a Yorkshire couple and the fluttery-eyed pig that allows Joyce and Gilbert Chilvers to power their way through the citizenry of Shepardsford so they can - literally and figuratively - secure a place for themselves at the table? The director Richard Eyre's winning response is to treat the material as a cross between Macbeth and Babe, the Scottish Play explicitly evoked on several occasions, usually by Sarah Lancashire's socially aspirant wife (pictured below). Is it any wonder that banquets are crucial to both scenarios?

A mild-mannered chiropodist who would scarcely hurt a flea let alone slaughter a pig, Shearsmith's baby-cheeked Gilbert seems happier tending to the townsfolk's pedal extremities than following the commands of his status-obsessed wife, notwithstanding Joyce's repeated promises of rumpy-pumpy as a reward if things go to plan. It's 1947 "austerity Britain" with a Royal Wedding looming - yes, all equations to 2011 welcome - and Gilbert traffics in "hard skins for hard times", dreaming of a shopfront he can call his own. Joyce, for her part, nurses shimmering song-and-dance fantasies of the somebody she might possibly be, if only her mother (Ann Emery, late of Billy Elliot) weren't so malodorous and the local meat inspector (Adrian Scarborough, sporting a leather jacket and not much of a singing voice) weren't so nasty. Or should that be Nazi?

The characters are rich with possibilities that you don't get from most screen-to-stage transfers, of which this is among the more unlikely and charming at once. The opening, "Fair Shares For All", introduces the pinched, parched landscape of a none-too-egalitarian community, and it is soon followed by the blissful "Magic Fingers", whereby three of Gilbert's female patients offer a wistful paean to his curative ways with chilblains. Still to come are a fan dance, a wartime reminiscence that doubles as Andrews Sisters pastiche, and the most yearning of love songs in the title number, albeit one sung by the accountant Allardyce (Jack Edwards, delicious) to Betty the pig; not since Michael Jackson's sung encomium to a rat called Ben has a member of the animal kingdom enjoyed so plaintive a serenade.

The fate of the unlicensed (or so we learn) Betty occupies most of a second act that devolves into strenuous screwball farce in a manic quintet called "Pig No Pig" and may have more numbers than the material really knows what to do with, lovely though it is to find mention in the programme of a finale ultimo. That long-forgotten musical theatre component in itself harks back to the golden age of the genre to which Betty Blue Eyes acts as a (literally, at one point) Union Jack-waving variant, rather as if it had taken the tale of a pig for Mackintosh and co to embrace a musical belonging in structure and sentiment to the pre-Cats era. (Stephen Mear's choreography pays witty if brief visual homage to Les Mis near the end of the first act, just as Oliver! - a Mackintosh mainstay - gets referenced elsewhere in a fleeting "oom-pah-pah".)

That we have 21st-century finesse available to us allows for the seamless contortions of Tim Hatley's masterly set, the clumps of green fringing the borders hinting at the promise of some vaguely obtainable Elysium beyond the parched greyness of the brickwork on view. Hatley, too, must take credit for the remarkable first-act costume change of Lancashire in faux-firebrand mode, the actress's clarion voice and expert timing the performance revelation of a night in which the women are more vocally confident than the men. Nor, to Lancashire's credit, does she overdo the Smith-isms (as in Maggie), tempting though that would be.

Those who've followed Eyre's career will delight in the reuniting of several of his erstwhile National Theatre stalwarts, Scarborough included, and so what if fellow Racing Demon alumnus David Bamber isn't really stretched by the part of Dr Swaby, the show's resident anti-Semite? It's the snobbish Swaby who leads a number about Britain's post-WWII decline that eventuates in a parade of men having a pee - an image that, as it happens, isn't especially out of place in a show whose harmonies at one point sing the virtues of apple sauce and at another posit the crazed Scarborough as a would-be Picasso. No, make that Pigasso: the show does, so why shouldn't we?

That the accomplished, always pungently quirky book arrives courtesy of two Americans, Ron Cowen and Daniel Lipman, is no stranger than My Fair Lady and Sweeney Todd owing much of their existence to Yanks despite their deeply British subject matter. Like all successful musicals, Betty Blue Eyes transcends nationality to take its characters on a journey of self-realisation accompanied here at the show's climax by the sound of Kylie Minogue, of all people, pouring forth from the blissed-out, animatronic Betty. And if the specifics of the piece involve Duchess of Pork jokes and lyrics about "offal" and "crackling"? As no one knows better than Mackintosh, it takes all kinds of musicals - and subjects - to bring home the bacon.