In England at the moment, everyone is gloating over Edwina Currie's revelation that she had an affair with John Major in the 1980s. For my overseas readers, I should explain that Mrs Currie was a Conservative politician until she lost her seat in the 1997 General Election. Long before losing her seat, she had wrecked her career by an unwise statement by which she single-handedly drove the British poultry sector to the edge of bankruptcy. Again for my overseas readers, I should explain that John Major was—Edward Heath always excepted—the worst peacetime Prime Minister of the 20th century. With his lack of political judgement over Europe, and his lack of political judgement in appointing a pack of sordid non-entities to office, he led the Party to an oblivion from which not even five years of Tony Blair have been able to rescue it. Now all the newspapers have gone back to discussing his judgment—how could he, they ask, have taken up with such a woman?

In my view, this is a silly question. There must be very few heterosexual men—perhaps very few men—who have not for at least a few minutes thought about having sex with Mrs Currie. She is a bright, attractive, charismatic woman. She stood out from the grey creeps who normally get advancement in the Conservative Party. As a politician, she was always reasonably brave and honest. In on the BBC Radio talk show with which she kept herself occupied after losing her seat, she certainly made a point of being nice to me whenever I was invited on as her guest for the evening—though, I regret to say, only ever by link to London from her studio in Birmingham. The only question of judgment that can arise concerns hers. What on earth could she have seen in a man like John Major? How could she have gone to bed with him? How more than once? He was not even Prime Minister at the time. I shall, I am sure, get over the shock of the newspaper revelations. But for the moment, I am compelled to think less of her than I did.

Enough of me, however—and, I suppose, enough of Mrs Currie and her lamentable taste in men. What I want briefly to discuss here is the relationship between sex and politics in this country, and to some degree in the rest of the English-speaking world. We live in an age where public expectations and personal behaviour seem more than usually to be in conflict. Politicians—especially in the Conservative Party, though not only there—believe that they are expected to maintain strict standards of sexual propriety. At the same time, they are surrounded by very powerful temptations to set those standards aside. At the same time again, they are watched by a media that has lost most of its old restraint in covering lapses from the perceived standard. The result is periodic waves of scandal, in which talk about "back to basics" is followed by gloating exposes of "sleaze".

It does not have to be like this. That it is like this is the fault of the politicians—those, that is, who lack an understanding of how the public mind actually works, or the courage to educate their constituency associations in how it works.

The truth is that most ordinary people are not censorious about the sexual behaviour of others considered purely in itself. I know hundreds of people fairly well, and scarcely one of them has conformed sexually to the standards set forth in the letters of St Paul. Nearly everyone sleeps around before finding a long term partner. Nearly every marriage is preceded by cohabitation—and this may last beyond the birth of a child. About a third of marriages in this country end in the divorce court—many for reasons where no one attaches any special blame to either party. In my experience, middle class parents never enjoin their children to contain or to marry. They talk instead about the avoidance of pregnancy or disease, and sometimes about avoiding emotional hurt from relationships. They do not expect their children to live like desert anachorites. Nor do they expect this of the politicians they elect to represent them or to govern the country.

What people do not like, and will not forgive, is the deception that adultery always involves. I am not laying down an absolute standard. There are often mitigating circumstances. A partner may be frigid, or a nag. There may have been a degree of temptation which it is not reasonable to expect anyone to resist. But it is deception that people dislike; and in the absence of mitigation, they will demand a politician's head with implacable force. Indeed, I cannot think of an occasion in my adult life when sexual revelations alone have destroyed a political career. Destruction has always followed from attendant circumstances.

Take, for example, the cases of Cecil Parkinson and David Mellor, who were rising politicians during the long period of Conservative rule. These men were not brought down because they had large sexual appetites, but because they satisfied their appetites in ways generally seen as disreputable. I will not go into the particular details of what they did, as at least Mr Parkinson—modern Peerages, by the way, should not alter forms of address—has a litigious reputation. But both men had, if only by implication, led their electors to believe they were faithful husbands. Both seem to have inflicted shame and other suffering on their wives. And so they came to nothing, despite their hopes and ambitions, and possibly despite their real competence in the offices they held.

Compare these cases with that of Alan Clark. Some while before he died, it was revealed that Mr Clark had seduced not only the wife of a judge, but also his two daughters, and that he had conducted simultaneous affairs with all three. There was a feeble effort to start an outcry, but hardly anyone thought ill of him. The general reaction was to admire his energy and to despise the judge for dragging his own disgrace into the media. No one thought ill of Mr Clark because he had never claimed to be other than he was. There was some sympathy for this wife—but this was muted by the facts that she plainly know what sort of a man she had married, and that he just as plainly did love her in his rakish aristocratic way.

Again, Peter Mandelson was brought down not by his taste for very young men, but by his apparently shady financial conduct. Chris Smith was never harmed by being openly gay. He came to nothing because everyone agreed that he was not up the job he had been given.

Now, I am not arguing here for the deeply corrupt European approach to sex and politics—where it seems that senior politicians can behave like Tiberius did on Capri, and the media looks the other way. Sexual conduct that involves deception should always be denounced, and should continue to bring and end to political careers. After all, as was asked at the time of the Cecil Parkinson scandal, if a man cannot tell his wife the truth, how can we trust him not to lie to us? But it would greatly raise the standard of political debate—and even reduce the amount of deception—if our politicians could stop imagining that we were still living in the 1950s, and took a hard look at what really was expected of them in their sexual conduct. If a politician is gay, or is living in an open marriage - where both partners have agreed to set aside the usual rules of fidelity—or is otherwise a sexually unusual, the best approach is to give up the pretence.

Again, I am not saying here that they need to advertise their lives to us. Nor should the media be indulged or even applauded whenever the muckrakers go to work. I disagree with Peter Mandelson for his politics and despise him for his general character. But I also despise the Murdoch press for its diligence in reporting his sexual tastes. These are not in themselves disgraceful; and before they were revealed, he had neither advertised nor denied them. They were therefore private.

It is the duty of a politician to promise to do what he sees as right by the country, and, if ever in power, to do what he has promised, and to do it competently. It is also his duty to conduct his private affairs in a manner that raises no doubts regarding his honesty and competence. Beyond that, what he does is not for us to question. That is the duty of a politician, and that is all most of us expect. One day, all those suited, brushed homosexuals who creep round Conservative selection committees, parading their church attendance and their alibi wives, will wake up to this simple truth. Until then, politics will be a scandal-ridden snakepit.

But none of this affects John Major. He stands revealed as a liar and an adulterer. His character is utterly blasted. I read that he will receive no further public honours. Bearing in mind what a dreadful Prime Minister he was, I rejoice that justice has been done. I remain disappointed that, of all the men in all the world she could have gone to bed with, Mrs Currie chose him. I also blame her, I suppose, for not having dished the dirt on him before November 1990. What a better place the country might be today.