Losing someone from a bygone era also means losing a vital reminder that things can be done differently. Perhaps that's why Diana Rigg's death last week left me strangely bereft. For she was not just a great actress who lit up everything she was in. She embodied a distinctive spirit that has become vanishingly rare. Maggie Smith, Helen Mirren, Joan Collins and Joanna Lumley are cut from the same joyous cloth; sexy, witty, dizzyingly intelligent – and in later life, mischievous grandes dames.

Watching The Avengers, which made Rigg a household name, is like stepping into a stylised pop-art poster. It presents a surreal England where everyone drives sports cars, the women are invariably gorgeous, with perfectly flicked-up eyeliner, the men stylish and charming. This gloriously over-the-top world hardly reflects the 1960s, which for most people were more gloomy than swinging, but it does mirror a more culturally carefree time.

Everything feels less serious. But behind the fun and froth is a feminist message. The film noir era often pitted women as men's intellectual equals, but it usually came via femme fatale tropes – murderess, manipulator or plain old bitch. Yet the female stars of The Avengers were pioneers in being simultaneously beautiful, intelligent and likeable. Driving around in her Lotus Elan, Peel quips haughtily to John Steed: "Apart from me, you're the best driver I know." Her fearsome intellect (in one episode she records a genius-level IQ), wit and self-assurance are as integral to her sex appeal as the leather catsuits and knee-high boots.

Granted, the 1960s had its share of basic female characters; numerous Plenty O'Tooles for every Pussy Galore or Tracy Bond, but compared to the fluttering glamour puss or gingham-frocked housewife heroines of the 1950s, this was remarkable. And unlike more explicitly "feminist" modern fare, the effort never feels laboured.