Something extraordinary occurs during the title song of “Betty Blue Eyes.” “There were never two more true eyes/ How I love this perfect pigmentation,” sings Henry Allardyce (Jack Edwards) to the one he loves, who is, er, a pig. Unsurprisingly, our hero Gilbert (Reece Shearsmith) looks on with serious skepticism. But midway through the song he joins in because he’s won over. Which is exactly what happens to the audience watching this nostalgic, big-hearted show that cheerfully catapults everyone back to the almost forgotten world of well-made musical comedy.

Like Alan Bennett’s screenplay for the 1984 cult comedy “A Private Function” upon which it’s based, Cameron Mackintosh’s new tuner, helmed by Richard Eyre, is decidedly English in both setting and attitudes. Closest in tone to the beloved British movies from Ealing Studios — “The Ladykillers,” “Kind Hearts and Coronets” — it’s a tale of Northern small-town snobbery in 1947 when chilly Britain was suffering major postwar austerity and stringent food rationing.

Everyone’s sagging spirits, however, are set to rise thanks to the impending royal wedding of Princess Elizabeth and Prince Philip. Seizing the opportunity for self-aggrandisement, local bigwig Dr. Swaby (sneering David Bamber) is arranging a celebratory private dinner for 150 important locals. He is secretly fattening an illegal pig to feed them all, but chief among those ostentatiously not invited are hen-pecked new podiatrist Gilbert and his social-climbing wife, Joyce (Sarah Lancashire).

As the event-filled plot proceeds, stakes climb thanks to the zealous presence of fearsome, Nazi-styled meat inspector Wormold (Adrian Scarborough, relishing his every mean-spirited moment), who is imprisoning all the local butchers for dealing in black market meat.

Having been called upon to attend to the pig in question, Gilbert is so snubbed by everyone, his wife included, that he steals the animal and attempts to hide it, promptly elevating everything into farce — a genre that routinely resists musicalization.

It says a very great deal for the sheer skill in the meshing of book, music and lyrics that the extended second act comic sequence “Pig No Pig” — where the (animatronic) pig must be kept hidden from an array of disparate, desparate visitors — is one of the production’s highpoints. The usual problem is that because singing takes much longer than speech, adding music usually slows everything down. Not here, thanks to tight rhythms, quick phrases and sharp multi-character writing.

Indeed, Stiles and Drewe, the tuner team whose previous hits include the gleeful “Honk!” and the additions to “Mary Poppins,” have come up with their best score that moves in and out of Ron Cowen and Daniel Lipman’s adroit book with impressive ease. The show consciously eschews blockbuster ambition but its attention to detail means it achieves rare and welcome charm.

Stiles’ music is wedded to its period. “Lionheart,” a big dance-hall jitterbug, is a winning Andrews Sisters-style swing number. And although the show is unwilling to trade authenticity for a take-home number, the melodies have staying power even in the many small ensembles, especially the winsome trio “Magic Fingers,” in which three female patients hymn praises to Gilbert’s professional touch. That typically strong ensemble writing is further enhanced by William David Brohn’s expert orchestrations for a 10-piece band including perky brass and evocative accordion.

Anthony Drewe’s comic lyrics do not attempt anything like the wild iconoclasm of, say, “The Book of Mormon,” but seizing the trim rhythms he nails key attitudes with nice wit. That’s encapsulated by “Another Little Victory,” the number where exultant Joyce crows, “Though the hoity-toity will be deeply shaken/ When they see that we are bringing home the bacon.”

Tim Hatley’s versatile succession of sliding shop-fronts and houses is set against a vista of green hills shown in streams of sunlight and extravagantly colored sunsets by Neil Austin’s lighting. It’s a highly effective contrast to his deliberately washed-out depiction of dowdy lives, as epitomized by the faded colors checks of Hatley’s pitch-perfect period costumes.

Lancashire cannot escape the echoes of Maggie Smith, who created the role on screen, but the contrast between reproving haughtiness and song ‘n’ dance prowess in her show-stopping “Nobody” is all her own. Shearsmith’s role of the worm that turned has sentimentality written all over it but his engaging candor as a performer, combined with directorial restraint, pull it back from the brink.

Helmer Eyre’s trademark expert handling of character extends into Stephen Mear’s zesty choreography. “It’s An Ill-Wind” — in which high-stepping, much millineried townswomen are scandalized by the smells coming from the hidden pig — is a delicious, accented take on middle-class horrors.

Bizarrely, this is not the first time that a cast has found itself singing “Kill the pig.” The unlucky souls in the legendary stinker “Carrie” sang it, but not for long. Happily resurfacing in this infinitely wittier show, the line looks set far to be sung for quite some time.

Betty Blue Eyes

Novello Theater, London; 1,080 seats: £62.50 $102 top

  • Production: A Cameron Mackintosh presentation of a musical in two acts, music by George Stiles, lyrics by Anthony Drewe, book by Ron Cowen and Daniel Lipman based on the Handmade film "A Private Function," original story by Alan Bennett and Malcolm Mowbray, adapted from the screenplay by Bennett. Directed by Richard Eyre.
  • Crew: Choreography, Stephen Mear. Musical direction, Richard Beadle. Sets and costumes, Tim Hatley; lighting, Neil Austin; sound, Mick Potter; musical supervision, Stephen Brooker, orchestrations, William David Brohn; dance and vocal arrangements, George Stiles; production stage manager, Simon Wood. Opened, reviewed April 13, 2011. Running time, 2 HOURS, 35 MIN.
  • Cast: Gilbert Chilvers - Reece ShearsmithJoyce Chilvers - Sarah LancashireDr. Swaby - David BamberHenry Allardyce - Jack EdwardsMother Dear - Ann Emery Francis Lockwood - Mark Meadows Inspector Wormold - Adrian Scarborough Sergeant NobleIan - ConninghamMrs Roach, Kitt, Princess Elizabeth - Annalisa Rossi With: Rachael Archer, James Barron, Dan Burton, Neil Ditt, Kirsty Hoiles, Christopher Howell, Andy Mace, Claire Machin, Laura Medforth, Hollie Taylor, Gemma Wardle. Musical numbers: "Overture -- Austerity Britain," "Fair Shares for All," "A Place On the Parade," "Magic Fingers," "Magic Fingers" (reprise), "Painting by Heart," "Nobody," "A Private Function," "Betty Blue Eyes," "The Riot," "Lionheart," "Steal the Pig," "Entr'acte -- The Pignap," "Another Little Victory," "Kill The Pig," "It's An Ill Wind," "Pig No Pig," "The Kind Of Man I Am," "Since The War," "Betty Blue Eyes" (reprise), "A Private Function" (reprise), "Finale Ultimo -- Confessions," "Magic Fingers" (reprise)