Death and taxes, Benjamin Franklin once said, are the only certain things in life. I’d like to add one more to the list: at some point in a woman’s life she will be told she should wear a safari jacket. Not when she’s planning a trip to Africa, but when she turns 40. She will also then probably be told she should invest in a peasant skirt and something called a “naval blazer”. Disappointingly, these tips are part of what I call age-dictated style: when clothes are divided up according to what is “appropriate” in each decade of a woman’s life.

In your 20s, you should be wearing denim miniskirts and colourful sunglasses. In your 30s, you should graduate to a tailored suit. By your 40s, of course, you’re embarking on safaris and when you reach your 60s it is time to get some “investment pieces”, which usually turn out to mean very boring but expensive plain coats and wide-legged trousers — think Helen Mirren.

Sarah Jessica Parker, on the other hand, has been condemned for daring to wear dresses that don’t make her look like the Queen despite being over 40. In the film version of Sex and the City, Carrie’s planned wedding is to be covered in Vogue’s Age Issue, an annual special that is genuinely produced by Vogue. “I want you to be featured in the magazine as the 40 year old — and here’s the brilliant twist — bride,” grins her editor. Get that bride a safari jacket! The only time a woman looks wrong in her clothes is when she is uncomfortable, either because she has bought into the idea that once she is over a certain age she should only wear sacks, or because she has been brainwashed into believing that a woman is only attractive when she is 25 and therefore is consciously trying to dress that age. When a woman dresses in a way that makes her feel comfortable and confident — that is when she looks her best.

Fashion should not be some form of checklist: if you are this old, you should wear these trousers. It should be about dressing in a way that reflects the individual wearer, not their age bracket. But when a fashion magazine is not just condoning ageing but suggesting that it need not be a dictating force in women’s lives, it’s hard not to feel just a tiny bit optimistic.