The most exclusive guest list of the decade included Frank Sinatra and new wife Mia Farrow, photographers Cecil Beaton and Richard Avedon, Oscar de la Renta, various Kennedy family scions, the Duke and Duchess of Windsor, Norman Mailer, Lauren Bacall, Andy Warhol and President Lyndon B Johnson’s daughter Lynda – complete with secret-service bodyguards dutifully wearing black masks.

DRESS CODE: Black tie and black masks for the men, white dresses and masks for ladies (although some deviated from this). A young Halston designed many of the attendees’ outfits, with Dior, Givenchy and Betsey Johnson gowns also featuring heavily. Farrow stood out from the crowd with her ultra-modern cropped hairstyle (which was cut for Rosemary’s Baby), white shift dress, white butterfly mask and long gloves.

CHIC FACTOR: It was the night that 16-year-old model Penelope Tree arrived. Like a witchy waif with her mask, black tunic and tights, and trademark poker-straight bangs, she looked otherworldly – something that wasn’t lost on Cecil Beaton and Richard Avedon, who decided on the spot they’d make her a fashion star.

TALKING POINT: The one guest who refused to wear a mask? Andy Warhol, of course. Meanwhile, attendees marveled at Lauren Bacall's dancing – the floor cleared so people could watch her cut loose, and the fact that spaghetti and meatballs were on the dinner menu – with all those beautiful white gowns?