Celebrity perfume is beginning to smell a bit dodgy – shares in Elizabeth Arden have plunged 25 per cent and the beauty giant has cited a bigger than expected decline in celebrity fragrance sales.

There are more than 500 celebrity perfumes released every year. Pope Benedict XVI has one. Cher Lloyd has one. Donald Trump has one. Bruce Willis has one. Peter Andre has one. Nick Clegg has one (maybe).

Unsurprisingly, the market is saturated. Even stars you might have heard of are finding it difficult to shift their aroma – Justin Bieber and Taylor Swift, in particular, who are being blamed for Arden's massive sales slump.

Bieber has The Key, a sickly blend of floral unpleasantness that claims to 'channel Justin's authentic voice that inspires his millions of dedicated fans to believe – to believe in themselves, to believe in their connection with Justin and most of all, to believe that their dreams will come true'.

It appears that pleading guilty to misdemeanour charges of careless driving, resisting arrest and vandalism, even if you plead in an 'authentic voice' doesn't shift perfume off shelves, especially if parents are paying.

Taylor Swift hasn't committed any such offences, unless you count the heinous crime of being a good role model to young women, but no one likes her fragrance, Wonderstruck, either, even though it is 'a charming and sparkling surprise of vibrant fruits, kissed by a bouquet of soft petals and a touch of sweet indulgence.'

How do you get the gig writing this literary gold?

But then again, One Direction's fragrance – Our Moment – remains the fastest-selling perfume of all time (last Christmas, The Perfume Shop sold a bottle a minute) and Elizabeth Arden's biggest celebrity seller is Elizabeth Taylor, who died three years ago.

Astonishingly, the key to selling perfume is creating one that doesn't smell as if you should be applying it liberally to your toilet bowl or using it to kill mosquitoes: Liz Taylor and One Direction's scents are OK. Beiber's smells like unattractiveness looks when in order to sell bucket-loads, it actually needs to smell like youth looks.

Scientists have concluded that in particular, the scent of pink grapefruits on a woman can give her an impression of youth. Just imagine, therefore, how young people would think you were if you hollowed out three or four and wore them as a citrus bikini and a jaunty hat. I suggest you try it forthwith.

The concept works on the basis that people, men in particular, associate certain scents with certain ages and can therefore be fooled into thinking women are younger if they detect a 'youthful scent' around them.

Women are slightly harder to trick. We associate the 'youthful scent' of a younger man with a great deal of cloying Lynx worn in lieu of bathing, or of a pervasive aroma of wet trainers, four-day-old polyester school shirts and egg sandwich-flecked bum fluff.

Even given the superior olfactory know-how of women, the only way I can imagine any perfume really helping you appear younger than you actually are is if you spray your date in the eyes with the perfume as soon as he arrives to pick you up.

Then, like Cinderella waiting for midnight, you'll have to keep watching your man until the blinding effect starts to wear off at which point give it to him with both barrels with as many blasts as it takes for him to agree that you look as if you're only 22.

Because I have a magic portrait ageing on my behalf in the attic (I'm actually 83), I don't need gimmicks or trinkets to help me look any younger or more desirable, and any lurking persistently around the tropical fruit section at supermarkets is, I promise, purely incidental.