Lucy Kellaway

Last week I discovered that I am a feminist, after all. Until then I had thought that women who did professional jobs were a privileged group who should stop complaining. But now I've had a slight rethink. What brought this on was neither hard evidence nor personal experience, but something entirely shallow: a 62-second advertisement for Pantene shampoo.

The new ad is set in a modern office in which we see men and women doing the same things, only with different labels attached to them. So the man is a “boss”. The woman is “bossy”. The man who works late is “dedicated”. The woman is “selfish”.

Written down, this sounds crass. But when you watch it – which you must do, if you have not done so already – you will find yourself singing along to “Mad World” and thinking: yes, double standards still exist. And yes, they still matter.

The ad was made for the Philippines, and might have stayed there had it not been noticed by Sheryl Sandberg, Facebook's chief operating officer, who declared it to be a top-notch example of "leaning in".

Now it has gone viral and I keep watching it over and over again, forcing my male colleagues to watch it too. But as I saw it for the fifth time, I stopped liking it quite so much. It is feminist – which is good – but it is also hairist – which is less so. All the women have lovely, luscious hair that they toss about – thus discriminating against those of us working women who have no lustrous locks to toss.

You could say that as it is pushing shampoo, it wouldn’t do to show people with visible roots and fringes that stick up. But then I thought: as Dove used oldish and largish women in its “Real Beauty” campaign, why can’t Pantene use real women with real (ie problem) hair?

Only then I thought about the world's most successful business women. They don't have problem hair, or, if they do, they have found a solution to it. Take the latest corporate female superstar: the 51-year-old engineer from Detroit who last week became the first woman to lead a car company. In her photos, Mary Barra has long, shiny, glossy hair falling prettily to her shoulders. Everyone has commented on how smart the new leader of General Motors is, and admired her delightful plain talk in saying "no more crappy cars". But no one has yet praised her hair.

This may be because among her peers she is not unusual. A hair audit of leading women executives in the US goes like this. Ms Sandberg: great hair. Angela Ahrendts: sensational highlighted locks, artfully ringleted. Marissa Mayer: perfect blonde tresses. Only Indra Nooyi and Irene Rosenfeld have gone for short, practical styles, and even they have every hair in place.

Ms Barra's shining locks may have escaped comment because people think it is sexist to go on about it. But hair is a feminist issue and should be talked about as an important inequality between men and women. The good blow-dry that women need every day is a haemorrhage of time that puts them at a disadvantage to their male counterparts, many of whom have no hair at all. Dan Akerson, Ms Barra's predecessor, had a highly convenient bald dome that must have taken all of one second to dry with a towel.

Time is money. Mr Akerson was paid $11 million a year, which works out at about $2,500 an hour (assuming he worked 300 days a year and 14 hours a day). So the opportunity cost of a half-hour blow-dry for long hair is $1,250, which comes to $250,000 a year, assuming 200 blow-dries are needed. And that doesn’t include the king’s ransom demanded by the hairdresser.

However, shareholders need not fear: good hair is worth every cent. The other day I gave a speech at a black-tie awards dinner and on the advice of a female colleague took myself off for a blow-dry first. It had never occurred to me to do such a thing before as I was brought up to think that was silly and frivolous. If you looked like a scarecrow, so be it.

So I went to the hairdressers for an operation that took 45 minutes and cost £40. After the application of an extraordinary amount of "product" and a lot of tugging and pulling I had an enormous helmet on top of my head. Bingo. I was invincible. I was Margaret Thatcher for a night. Forget coaching. Forget power dressing. For an injection of confidence straight into an artery, a blow-dry does the trick.

Pantene’s arch rival L’Oréal has encouraged a generation of women to buy its beauty projects teaching them to say: “Because I’m worth it.” If Pantene is now pitching to working women, it should trump that with: “Because it’s a damned good investment.”

Copyright The Financial Times Limited 2013.