Say what you like about Madonna, she doesn’t look like she is 49. Not only that, she has permanently altered the way women over 40 are perceived and is tireless in her crusade. It’s hard work and we know it: the ashtanga, the Callanetics, the Power Plate, the raw food diet, the trainer she shares with Gwyneth, the endless trips to the dermatologist (I think you know what I’m saying). Madonna puts in the hours, and that is why she looks so young.

It had all seemed beyond the average mortal and then something surprising happened. Madonna arrived in Cannes wearing Chanel couture: fab in theory, but, woah! She looked like the Olsen twins’ grandmother. At a stroke, we were reminded there is one crucial element of looking fabulous for your age, and it counts for way more than being fit as a butcher’s dog: the right fashion choices.

It’s not easy to judge what will or won’t be ageing. A long, slippery, sequined number and some killer heels sounds spot on (not too try-hard, but suitably de luxe). However, long and slinky can turn brassy and Bet Lynch if you don’t have the freshness and height to carry it off. Remember Posh in that white Armani gown that looked like it had walked off the set of Dynasty? Suddenly she was Nancy Reagan at a White House fundraiser and roughly 20 years older than her real age - and the hair didn’t help. It's grown-up clothes, hair, make-up and accessories (“age-appropriate” elegance), not the risky stuff, that make you look like mutton.

As it happens, Madonna did risky at Cannes, too - spray-on over-the-knee boots and black leather fingerless gloves - the kind of hard-edged, rebels-only stuff women over 35 are meant to avoid, along with miniskirts, short shorts and strapless vests. As well as looking younger than she did in the Chanel, she looked good, despite ticking all the wrong boxes.

Meanwhile, Gwyneth is getting her comeback look bang on. Mindful that in Hollywood “there is always somebody younger or prettier”, Gwynnie has done the hard-slog training and the raw diet, but, crucially, she has nailed the fashion ticket in the shortest dress, the strapless dress, the one-shouldered dress and a succession of fierce heels. Every time she gets in front of the cameras, she knows the challenge is to look youthful, which means not just fit, but fearless and hungry – and that’s where the Alexander McQueens and Giuseppe Zanottis come in. Swap the shoes for Madonna’s standard f***-me pumps (which now look so tame, they are practically mother-of-the-bride) and you would have a different Gwynnie: elegant and pretty, but no longer competition for her twentysomething peers. Perhaps if Madonna had teamed the Chanel dress with scary Terry de Havilland platforms, she would have got away with it. Maybe not, though.

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