The Boris, Cecil and Jeffrey club

When an alpha male is also a politician, Darwinian instincts won't be easily reined in

There is more esprit de corps among women than we realise. We are particularly sisterly to women in trouble, so while the betrayed wife gets reams of supportive rhetoric, the seducer receives all the hate mail and nasty labels such as "slapper". This does not mean we females are nicer or more moral than our fellow men, only that we instinctively wreak our competitive vengeance on the sexually successful woman while sympathising with the rejected one. It is salutary to see the contrasting pictures of Boris Johnson's wife and mistress in the current spate of adulterous scandal; Marina in high-necked, cover-up, winter woollies, while Petronella is shown in frivolous party-gear, all low necklines and stocking tops, fringes, flesh and fancy jewels.

We all know that men are born to stray, but mathematically there must be an equal and opposite number of women opportunities to accommodate them. If only women really could form a freemasonry which swore not to steal another woman's man, what a tidal wave of sexual energy would be released to perform works of art, feats of sporting endeavour and flights of poetical fancy. But where sex is concerned we are all victims of primeval hard-wiring: cunning, prowling gonads rule; secrecy and scoring prevail.

I am Britain's most famous political ex-wife. I was a Westminster wife for nearly 30 years and saw the effect that the grand corridors of power had upon the ego of multiple men. Combine this with the all-too-eager hangers-on who are mesmerised by the messages of power and you have a recipe for disaster.

Boris is the quintessential alpha male. At 40, he has two marriages under his belt, four children by his current wife, and has impregnated his mistress once, if not twice. Not bad going. In stuffy Darwinian speak, men seek power to gain reproductive rewards. On the face of it, it seems an unlikely postulate. Yet in an intriguing anthropological study, it has been shown to be true. It should be understood that men are exquisitely oblivious that they are driven by evolutionary imperatives. Yet they have an inbuilt, mathematically precise understanding of how their power translates into the number of women available to them. Then it's up to chance and contraception; but high-flying men are notoriously averse to condom-use, so the odds are on that they'll father more sprogs than average.

Their power must be societally authorised, and our current one does not approve of politicians having mistresses. So Boris's career has been cut short in mid- parabola. But never fear or feel too sorry. He has all the appurtenances, and will reincarnate like Cecil Parkinson, Jeffrey Archer, David Mellor and countless others. It's curious how in Tory circles infidelity (or lying about it, believe that if you will) is a resigning issue. New Labour has been more broad-minded - witness the David Blunkett allegations - unless the indiscretion is too wayward or colourful.

The task of sexual selection is a relatively easy process for men: youth, health, beauty, all testify to the senses that here is a fertile female. The equivalent task for women is infinitely more difficult. Health indicators are vital, but more than that is needed. Is this man a good hunter - in a modern setting? Will he stand head and shoulders above other males? Excelling in some sphere, leader qualities, capacity to talk and dominate a gathering are all advantageous. But a woman must match his power to her own desirability, for aiming too high is disastrous. The task is easier if you choose an older man, for he will have arrived; he will carry his badges of worth about his person.

Boris is a big chap, clever, witty, funny, famous, an MP who performs well to camera. His idiosyncrasies add to his attractions: his boyishness - youthful appearance is always an advantage - blond hair which looks as if he's cut it himself, his humorous self-deprecation. He's pretty well loaded with desirable appendages. Yet the deference and privileges received in the Palace of Westminster tend to inflate a man's idea of his own importance, and this particular man obviously feels above the rules that govern the plebs.

Petronella Wyatt, a socialite and daughter of fame and money, could on that account gauge her chances highly. At 35, though, she is on the brink of middle age and failing fertility. Her mother clearly thought so and deemed Boris a good catch, in spite of his being burdened with a family. Still, at a level of society where adultery and fission-fusion relationships are legendary, an existing wife was not an insuperable problem.

Lady Wyatt's unguarded remarks to newspapers sound like a predatory mother from Austen or Trollope. It was time her daughter was married. The daughter schemed that Boris would leave his family for her - indeed the reason Petronella went out with him was because he promised marriage. All this shrieks of desperation in both mother and daughter: how readily do women believe those promises when made in the intimacy of detumescence.

Indeed, women's hormones rush around creating bonds during those moments, ensuring they are gullible and hyper-receptive. Heaven knows how confused these hormonally driven messages become when a party girl is involved.

While feeling sorry for the wife, I cannot help remembering a time some 11 years ago when she performed the same trick on Boris's first wife, Allegra Mostyn-Owen. She became pregnant and got her man. Maybe that was what led Petronella to rate her chances highly of doing the same. It is to be hoped that the four children will weigh most heavily in the balance as to where Boris's wandering ways will come to a halt.