Terence Rattigan’s “lost” play After the Dance begins with a butler opening the French windows while a young man taps away on a typewriter and an older man snoozes on the sofa under a copy of The Times.

So far, so familiar, audiences must have thought in the summer of 1939, when the play, Rattigan’s second, opened in the wake of his smash hit Riviera comedy French Without Tears.

But war loomed, the play turned sour and audiences stayed away: it closed after just 60 performances, despite a critical huzzah, and has not been seen since, save for Dominic Dromgoole’s well-reviewed touring revival for the Oxford Stage Company eight years ago.

Thea Sharrock’s NT production is a revelation. The game is up for the bright young things of the 1920s, stewing in alcohol and partying on with a suicidal frenzy as Rattigan zooms in on the London flat of the Scott-Fowlers, where the young man, Peter, is typing up the latest history book of David while Joan keeps the cocktail cabinet fully stocked and much visited.

This couple, beautifully played by the effortlessly smooth Benedict Cumberbatch and the gorgeously febrile Nancy Carroll, are ignoring all signs of change and decay, David literally so in the case of his battered liver. Forced to have a medical examination by Peter’s fiancée Helen (Faye Castelow, bright-eyed and feisty, resembles a young Sarah Miles), David gives up the drink then gives up Joan.

The consequences are disastrous but also inevitable, as another party scene blazes to unexpected and brilliant life, and the recurring, plangent tones of Al Jolson’s “Avalon” overlap with the ominous intervals of a Puccini aria from Tosca. The old sofa boy – Adrian Scarborough is the perfect hanger-on, kept in booze for his good company – delivers a harsh analysis of the real world which involves jobs and babies in Balham and is forced to accept work himself in Manchester with a window-cleaning business.

This shifting of social parameters with an acid nostalgia for the old world of hedonism and frippery is brilliantly done in the writing and carried through not only in the performances, but also in Hildegard Bechtler’s luxurious mansion flat, bathed in sickly morning light by Mark Henderson.

This is one of the most significant, glorious and enjoyable productions in the National’s history. It’s like early Noel Coward mated with mature David Hare. And it’s studded with lovely cameos from Giles Cooper as a baffled young medic, Pandora Colin as a “stinking” drunk vulture flying in from Le Touquet, Nicholas Lumley as the unflappable butler and Jenny Galloway as a stern, monosyllabic new secretary in the third act.