WHAT does "age appropriate" mean, please? I was at Waterloo Station this week when a very striking woman probably in her 40s (though I am a poor judge of age, amongst other things) strode through the concourse on the way to her train. She was head-turning in a way that few people are in these dull and grey times.

Taking her cue from the summer weather and from the Mad Men series, she wore a 50s inspired green flowered cotton frock pulled in at the waist with a wide yellow belt and billowing out from her generous hips. Her hair was long and dyed a rich red and emphasised her towering pink suede shoes. I thought she looked stunning and happy and she made me smile just for the sake of it.

Three women, watching her, tutted and one said: "Hardly age appropriate, is it?"

They had in common that they had never turned a head in their lives or, I suspect, made anyone smile with the simple joy of colour and vitality.

So what is it appropriate for a 40-year-old woman to wear? Or, come to that, a 60-year-old? Presumably it is something about going with the norm, not standing out from the crowd, striving to be invisible, denying the individual in oneself.

It was never thus in the 60s. In my world the beauty of being able to make your own clothes meant you could create your own look, inspired by magazines and film stars, yes, but owing more to imagination and fancy dress than peer group pressure or a need to conform.

Setting aside the obvious need for children to look like children and the value of the uniform at school and the workplace, I think it is time to value the eccentric. If you see something in a shop in all sizes from eight to 26 then it isn't for you. How can it be? If you buy something and go to your wardrobe and find you have something similar or in the same colour then take it back. If you buy something new and you aren't sure about it and your spouse looks askance and frowns disapproval then you are probably along the right lines.

If you find yourself screeching to a halt at a shop window and eyeing up a cardigan or flat shoes and thinking, 'they look comfy', then pull yourself together and tap into the kittenish in your nature. Think Jane Birkin, Charlotte Rampling, Meryl Streep.

And gentlemen, however conservative you feel yourself, resist the temptation to roll up the sleeves of your business shirt (like Cameron), and instead follow David Beckham's example. Tuck a rascally spotty silk handkerchief into your top pocket. It could do wonders for you. After all who wants "appropriate"?