The butler did it. That’s not a plot spoiler, it’s the diagnosis of the cause of the tangible feeling of happiness filling the giant Olivier auditorium in under a minute from the start of Nicholas Hytner’s splendid revival of “London Assurance.” As funny as it is silly — which is very — the play was a smash hit on its first outing. That was in 1841. History looks likely to repeat itself.

The character in question is Cool, a gentleman’s gentleman played by a baleful Nick Sampson with almost impossibly high status. Painstakingly erect of carriage and lifting long-suffering forbearance into an art form, Sampson makes his entrance so, well, assured that the audience relaxes into laughter from the mere lifting of his chin.

Harnessing the energy supplied by Cool’s delicious milking of the “textual revisions” — the National’s euphemism for comedy rewrites by playwright and erstwhile stand-up Richard Bean — Hytner’s production moves fluidly into the play proper.

Hytner’s sparky cast brings so much immediacy to Boucicault’s collection of opposed town and country characters that even the expository opening scene achieves comic liftoff.

Everything revolves around aging man-about-town Sir Harcourt Courtly (Simon Russell Beale). A dedicated follower of fashion, he claims the age of 39, is actually the wrong side of 50, and is overexcited about his impending marriage to Grace (Michelle Terry), who is all of 19.

The preposterousness of his proposal is underlined by Beale’s blissful comic turn. A high-whipped confection of preening and tottering, he makes Courtly’s self-delusion both extravagantly comic and, bizarrely, charming.

He’s matched by a redoubtable, cigar-smoking Fiona Shaw as horsy Lady Gay Spanker. Braying, bewigged and bewitching, she swaggers about like an outraged pepper pot.

Yet, while their superbly staged scenes of farcical lovemaking are the production’s comic highpoint, the success of the show as a whole depends on a similar level of precise, unforced comedy that runs throughout the ensemble.

Shivering in his nightgown, veteran British actor Richard Briers makes a delightful meal out of Lady Spanker’s put-upon, Francophobe husband. And rising National Theater stars Paul Ready and Michelle Terry, in particular, bring zest and even unexpected depth to the young lovers who, as expected, go through misunderstandings before emerging triumphant.

Despite the comic gusto of the script, most theaters balk at “London Assurance,” not least because it demands a large cast — it’s played here by 18 actors. It has been a long time since the National mounted anything as unashamedly daft as this, but the production, wittily designed by Mark Thompson, vindicates the decision to revive it. This production may point the way to equally large-scale theaters taking another look at the play.

London Assurance

National Theater, Olivier, London; 1,129 seats; £42.50 top

  • Production: A National Theater presentation of a play in two acts by Dion Boucicault. Directed by Nicholas Hytner.
  • Crew: Sets and costumes, Mark Thompson; lighting, Neil Austin, sound, John Leonard; music, Rachel Portman; choreography, Scarlett Mackmin; production stage manager, Jane Suffling. Opened, reviewed Mar. 10, 2010. Running time: 2 HR, 40 MIN.
  • Cast: Sir Harcourt Courtly - Simon Russell Beale Charles Courtly - Paul Ready Max Harkaway - Mark Addy Grace Harkaway - Michelle Terry Lady Gay Spanker - Fiona Shaw Mr. Adolphus Spanker - Richard Briers Cool - Nick Sampson Richard Dazzle - Matt Cross Pert - Maggie Service Mark Meddle - Tony Jayawardena With Fiona Drummond, Mark Extance, Richard Frame, Junix Inocian, Simon Markey, Laura Matthews, Prasanna Puwanarajah, David Whitworth
  • Music By: