The biggest change in fashion in the past decade has to be that the rules have loosened right up and the don'ts have now shrivelled to almost nothing. Even so, the old concept of dressing your age just won’t fade away. In spite of the evidence all around us that how you look in clothes bears no relation to the year you were born — Michelle Obama sleeveless on the cover of US Vogue, Elle Macpherson looking fitter in a minidress than models 10 years her junior, Helen Mirren hitting the beach in her red bikini — we still fall back on the same old mantras: fortysomethings shouldn’t wear short skirts; bikinis are undignified past 38. Every time we open a magazine, we see confirmation that what counts is not age but body shape and confidence. But still those rules that applied to the pre-Pilates-and-sushi generation keep sucking us back to what is and isn’t age-appropriate.

The time has come to lay the old taboos to rest: we can wear anything, we already are and, what is more, we really should, because the one thing guaranteed to age women faster than sun exposure is scuttling for the safe ground and covering up in chiffon shrugs. Of course there is a point at which women look ridiculous in hot pants. But thigh boots? If your legs are long enough, why not? Yes — as Sadie Frost discovered — you know it’s time to lower your hemlines when your kids start complaining. But that doesn’t mean putting away your arms, your wedges or even your lower thighs. What we need is advice on how to wear the banned stuff better, because, by and large, we know when we look ridiculous (we can work that part out for ourselves), and we can see that Obama looks a lot fresher going sleeveless than in a nice, safe cardie. So here are some of the classic no-we-can’ts — and lots of reasons why we can.

Things that always make you look older, no matter what

- Shoes from Ecco

- Round-neck cardies

- Below-the-knee hemlines

- Chiffon (post-40)

- Bouffant, stiff hair (see Agyness at the Met)

- Sugar pink

- Pastel pashminas

Things that remind people you are trying to look young (so wear with caution)

- Biker jackets

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