If you’ve ever asked, “What’s all the fuss about” when confronted with Restoration comedy, ask no more.  See “The Relapse,” written in 1696 by John Vanbrugh, staged with style by Trevor Nunn, and performed by a consummate group of actors led by Alex Jennings as Lord Foppington.  At the National Theatre’s Olivier home, within a clever set by Sue Blane that duplicates the candle-chandeliered Restoration stage, this is a vibrant production, pulsing with life, with song and dance, swordplay and musketry,  town and country, and ending with a marriage masque.

“The Relapse” is Vanbrugh’s cynically comic riposte to the morally uplifting conclusion of the then hit comedy “Love’s Last Shift” in which playwright Colley Cibber worked out an ingenious combination of audience-appealing vice with virtue, as required by the moral reform campaign of the new administration of William and Mary. Vanbrugh couldn’t stomach Cibber’s hypocritical ending, in which rakish hero Loveless, after whoring, drinking, and gambling, repents and is forgiven  by his  long-suffering but faithful wife, Amanda.  In six weeks Vanbrugh wrote “The Relapse,” in which Loveless (James Purefoy), bored with good behavior, returns to his former ways.  Unlike the emerging sentimental drama, “The Relapse” is surprisingly modern.  Expressed in sophisticated, witty aphorisms that Oscar Wilde appreciated and adapted, it cynically exposes the hypocrisy that accepts marriage as a cover for adultery and applauds the outrageous as long as they are wealthy.

Not only did Vanbrugh take over Cibber’s married pair, but he also appropriated  the role Cibber wrote for himself, that of Sir Novelty Fashion, a self-indulgent, overdressed dandy. Elevating him to the title of Lord, Vanbrugh creates one of the most memorable comic characters of Restoration drama, Lord Foppington, the fop of fops, and as brilliantly acted by Alex Jennings, the centerpiece of this delightful comedy.

We first meet him as he is dressing for the day, attended by his tailor, milliner, and wigmaker, surrounded by mirrors (“I love to see myself all ‘round”), complaining that his periwig isn’t full enough on the sides, making him look fat-cheeked, like a trumpeter. Pouting and preening, with delicious delivery of his lines by Jennings, he asserts that the pocket of his coat is too high; when told that its height is appropriate for  his handkerchief, he reminds them that his page carries that article. Although this popinjay is in the House of Lords, the audience need not fear.  He outlines his day (“My life is a perpetual stream of pleasure”) in which he abjures reading or even thinking. At the theater, where he spends each evening, he sits with his back to the stage, so the audience can see him.  Afterwards, he drinks himself drunk and sleeps himself sober.

 Like any Restoration gallant, though even more dressy in his bows and furbelows, he lusts after pretty women. When he makes a play for Amanda (Imogen Stubbs) and finds himself in a duel with Loveless, he pauses in the swordplay to admire his opponent’s cuffs, and whimpers “my epaulet,” as it is deftly swept from his coat.  An attendant doctor notes that his wound is barely a skin graze, but when Fopppington offers him 500 pounds for a cure, the physician sweeps him off to his own home.  Other professions come in for satire as well, including clergymen.

While the city inhabitants are criticized for their gossip, deviousness, and immorality, the country folk fare no better.  Besides the main plot of Amanda and Loveless, who pursues her cousin Berinthia and carries her off for seduction (as she whispers a barely-audible ”Help”), the subplot concerns that Restoration favorite, two brothers, the younger good-hearted but penniless, the older selfish but wealthy. An unscrupulous homosexual matchmaker, hilariously interpreted by Edward Petherbridge, has arranged for Foppington to marry a rich country heiress, Hoyden, but double deals for profit, also promising her to brother Tom.

Tom’s visit to claim and secretly marry Hoyden introduces us to her father, Sir Clumsey Tunbelly, whose house is a rough fortress, manned by rustics with pitchforks and muskets.  Brian Blessed is ideal as the bumptious Tunbelly,  echoing his raging despot in television’s “Blackadder.”  The skittish Hoyden (Maxine Peake) cannot wait to leave her rural confinement for a life of intrigue in the city, aided by her Nurse (Janine Duvitski) and   chaplain (Paul Bradley) out of Shakespeare’s “Romeo and Juliet” via Hogarth.  Like Juliet, she is faced with not one husband but two.

 Hoyden opts for both, and at a sumptuous wedding gathering at Lord Foppington’s, he enters looking like the cake – all in white from mountainous wig and satin coat and breeches to pumps, placing a sparkler not on the hand of the bride to be, but on his own.   Amanda having thwarted an attempt on her virtue, all is resolved in a matter of minutes, and ends with a charming 17^th-century masque followed by dancing by the 26-strong company combining stately minuet with country clop hopping, and singing “Constancy’s an empty sound.”  Don’t miss “The Relapse,” which runs at the National Theatre’s Olivier Theatre, through November 17.  Schedule of repertory performances: www.nationaltheatre.org.uk.