by Lesley Thomas, The Times

Photo of Yoko Ono by Nick Knight from the latest issue of Vogue – on sale now.

How many people over the age of 30 look good in hotpants? What about 40? 60? How about nearly 80? Yoko Ono, the artist and widow of John Lennon, appears in the forthcoming issue of Vogue in tiny shorts, breaking all kinds of style rules (chiefly, never show legs and cleavage simultaneously) and looking quite fabulous — and not just for a 79-year-old. With her pixie haircut and sunshades perched on the end of her nose, Yoko shows taut thighs and a high bosom that couldn’t possibly be the work of digital retouching.

“Style is by no means all about clothes,” says Alexandra Shulman, the Editor of Vogue. “Nobody demonstrates more clearly independence and exuberance than Yoko Ono.”

Interviewed in the magazine, Yoko, a grandmother of two, is asked how she has maintained such a physique. Her explanation is: “Because I’m a performer. I do the performance.” Though Ono’s performance is, in this instance, for Nick Knight, the fashion photographer, she is not the first woman of pensionable age to put on such an impressive display.

Helen Mirren, 66, seems to have spent most of her seventh decade wowing us in bikinis and foxy red-carpet dresses. Jane Fonda, 74, rocked up at Cannes in a Versace gown last month.

Vera Wang, 62, the famously buttoned-up chic US designer, appeared in US Harper’s Bazaar earlier this year wearing high heels and a bathing suit.

Is “sexy at seventy”, “enticing at eighty” just for celebrities? Emma Soames, of Saga magazine, says there is a new generation who see no reason to stop following fashion, which sometimes dictates a flirtatious look. “There must be something in the air or the water because all around I see older women, over sixties, looking fabulous.”

Ms Soames, 62, says: “Women are enjoying it. So much more fun than dressing up when you’re in your thirties. It’s no longer about trying to keep up. These women are not trying to look youthful, they’re just trying to look great.”

It’s less about sex, more about fashion, she says. No one talks any more about mutton dressed as lamb.

“In your seventies you just have to be careful about parameters, keep things simple, don’t wear too many accessories.”

The New York fashion photographer Ari Seth Cohen has a style blog (and soon a book) called Advanced Style, packed with groovy grannies in edgy clothes.

Shirley Conran, 79, whose blockbuster Lace is about to be reissued, says we merely need to tweak our dress codes in old age. “I’ve just stopped wearing jeans. I think well-cut trousers are more appropriate. But I don’t want to look like an 80-year-old. I want to look sort of in the swing. I’m wearing Zara and Donna Karan. What most women of this age need is a white linen jacket.”

So will men have to raise their game? “Many will have to take a good look at themselves and get out the nasal hair clippers. It’s not that difficult for a man to look great when he’s older and grey,” Ms Soames said.