LAST WEEK I went to a party given by an old university friend. It was a jolly enough event, full of people I’ve known for more than 30 years. But as I left, I realised something strange: my successful female friends have started to scare me.

I then thought about the men at the party, most of whom were thinning on top and thickening around the middle. Not one made me feel even slightly nervous, even the ones with big jobs and even bigger opinions of themselves.

So what is it about successful women that makes them so frightening? Take the two scariest 50-something women in the world: Madonna and German chancellor Angela Merkel. The first has just released an X-rated video in which she grinds against the wall in bondage gear and lords it over a band of gyrating black men. The source of this fear is not exactly obscure, but kicked towards you in thigh-high boots.

Merkel’s scariness is quite different, and altogether more mysterious. She shuns the spray-on trousers – last week she was pictured in a demure pea-green jacket, uncomfortably similar to one I own. Her terror quotient has nothing to do with erotic capital but hangs around her like a halo in the cut of her hair and the way she purses her lips.

As a control experiment I have just looked at a picture of French president Nicolas Sarkozy, but instead of feeling scared I wanted to laugh – until I spotted his wife, Carla Bruni, loitering terrifyingly beside him. It’s the same with the Clintons: Hillary scares, Bill doesn’t.

If I think of my colleagues, a similar pattern emerges. Dame Marjorie Scardino, chief executive of Pearson, which owns the Financial Times, strikes a degree of fear into my heart in a way that her male predecessor did not. Many of my senior female colleagues are scary. Their male counterparts are pussycats by comparison.

I’m not saying that no men are frightening. If I was faced with Bashar al-Assad, I dare say I’d feel a bit uneasy on the grounds of his being a mass murderer. I’m sure Steve Jobs was also quite frightening, at least when he let rip. What I am saying is that I need a reason to find them so.

Only a few of the women who scare me do so for a reason. Margaret Thatcher and Anna Wintour, who are tyrannical on a world scale, are in this category. So too is Rebekah Brooks, with that flaming hair and flaming temper. She is far more terrifying than Murdochs snr and jnr put together, which is saying something as Murdoch snr is pretty scary.

But the vast majority of women who scare me have done nothing in particular to merit it. So what, exactly, is it all about? I’ve thought and thought and come up with half a dozen reasons. None of them is a complete explanation, but here they are anyway.

First, the scariness could be Darwinian. It is harder for women to advance, so those who make it have to be more fierce. Second, it could be women act scary to drown out the voice of their inner imposter. Or third, women may be frightening as they are harder to read. Unpredictability leads to anxiety.

Or it could be nothing to do with successful women and everything to do with how we perceive them. If we still expect women to be motherly, we are alarmed when they show the tiniest sign of not being so. Or it may simply be a product of scarcity. If you are rare, it’s easier to scare.

A final possibility is that it might have something to do with the women of our childhood. I remember going to a dinner attended by two men who played a senior role in UK foreign policy. At first the discussion was about Afghanistan, but over coffee it shifted to prep school, and it became clear that matron and her stool inspections inspired more fear than did the Taliban.

Whatever the reason, being frightening is hugely to women’s advantage. I know all sorts of women who get their way because their bosses are too terrified to say no. These women are not tyrants or nasty in any way. They may even be what counts as nurturing leaders but they just know when to give the look, the sharp word, how to hold their heads to make everyone – men and women – fall into line.

Writing this column has made me resolve to increase my own terror quotient. But before I begin, I’ve tried to gauge the starting point and asked a colleague to rank me on a terror scale from one to 10. Eleven, he replied. His eyes were shining as he spoke, which might have meant he was speaking from the heart. Or it could have meant he was joking. – (Copyright The Financial Times Limited 2012)