I must be an ad-man's worst nightmare. My friends all tell me that my fashion sense is pretty dreadful; my color sense is highly questionable and any sense of style that I show off is as often as not down to sheer luck than anything else.

For a long time, I have used the fact that I am partially colorblind as an excuse for my "fashionista faux pas." But if the truth be known, I cannot really get excited by the buzz that seems to be so common among the majority at large whenever the newest branding advertisement is released, or a brand special is written up by such fashion guru websites.

So the news that Brad Pitt is to be the new face of Chanel No 5 is not something that sent waves of excitement through me as I turned the news pages of a somewhat lethargic news day this week. And yet…

It is said that the 48-year-old movie star will make history as the famous scent's first male model, and is currently shooting his first campaign for the brand in London, for which he will receive a seven-figure sum. He follows in the footsteps of previous Chanel No 5 brand ambassadors such as Catherine Deneuve, Nicole Kidman, Audrey Tatou, and Ali MacGraw.

The story of the rise of Chanel No 5 passed into legend a long time ago. Up until the 1920s, traditional fragrances worn by women had adhered to one of two basic categories: "respectable" women favored the pure essence of a single garden flower, while those of "more suspect morals" chose the sexually provocative perfumes heavy with animal musk or jasmine.

What Coco Chanel did was to identify that the time was right for a third type of scent that would epitomize the liberated spirit of the 1920s, "reflecting her personality, something abstract and unique." It was the first commercial perfume blended from a mix of aldehydes, roses and jasmine.

It was launched on the fifth day of the fifth month in Chanel's Rue Cambon boutique in Paris, and its success was immediate. And in a 1954 interview, it gained further invaluable publicity, when Marilyn Monroe was asked what she wore to bed. The movie star provocatively responded: "five drops of Chanel No 5." The rest, as they say, is history. That perfume is now perhaps the most recognized scent in the world.

But given that Chanel No 5 is not that short of its centenary, why is it that it continues to captivate and grab market share while other brands, that were once considered invincible, have died? This is not just a phenomenon of the perfumery marketplace. Think of other world brand leaders such as Coca-Cola, Microsoft, Google or Mercedes.

With the advent of the Internet, the opportunity to market much more widely than was ever possible in the last century has made "super brands" both a possibility and a millstone for others, who now face competition from areas they never faced before.

Brands that rely on their longevity are now at real risk of being overtaken, overlooked or undermined. Past reputation is no longer a defense against the insatiable demands of today's markets. Unfortunately for marketers, the collective attention of consumers around the world continues to contract as information overload reaches ever new heights.

In Chanel's case, it is said that its continued success is due in no small part to the fact that it's a story of style over money. Anyone can have money, but only a few recognize style. The Chanel brand has always understood the irony of longevity: one must be current, even ahead of one's time, but never a slave to trend, and never just a reflector of fashion. As Coco Chanel herself is famously quoted as saying, "fashion passes; style remains."

The power of Chanel is its unbreakable link with Paris, which, as a symbol of sophistication and glamour, continues to shine as bright as ever. It has understood the need to be both accessible and yet to stand aloof. Everybody knows the Chanel brand, many aspire to it, and yet because of its cost, its haute couture is worn by very few. Fashion and trends come and go, but a classic brand like Chanel understands that timeless appeal is much more important than a passing whim.

So good luck to Brad Pitt and his mega-dollar contract with Chanel. But it leaves me wondering if his fiancée and long-time partner Angelina Jolie is a fan of No 5 and if she will be required to squirt the stuff liberally over herself to support her husband-to-be's latest deal. Any guesses what he will be handing out under the tree next Christmas?