THE SEXUAL exploits of Roy Cornes, the Birmingham haemophiliac with the Aids virus, scared many people, but especially newspaper editors. The discovery that Mr Cornes had allegedly passed on HIV to at least four women challenged the deeply held belief of some of them that Aids is a gay, druggie plague and therefore irrelevant to their nice, normal, heterosexual readers. Then, last weekend, the editors could breathe again. Mr Cornes turned out to like anal sex.

This practice, it would seem, is something only peculiar people do. And they more or less count as gays anyway, according to a doctor in the Daily Express: 'Generally a man who wants anal sex will be bisexual. ' The Sunday Times headline - 'New evidence casts doubt on Birmingham Aids scare' - implied the rest of us were off the hook; a feature on Mr Cornes's lifestyle hinted darkly at an underclass, having weirder sex than everyone else. The News Of The World found the activity so abnormal that it was unable to refer to it any more directly than as 'dangerous kinky sex'.

Leaving aside the relative Aids risks attached to different orifices (anal intercourse is generally, although not universally, believed to be more dangerous), how reasonable are these assumptions that heterosexual sodomy is practised only by a tiny minority of strange people?

Not at all, according to the little evidence available. The Kinsey Institute's 1990 New Report on Sex reviewed seven studies over 40 years 'to estimate the number of women who have experienced anal sex at least once'. It concluded: 'Our conservative estimate is that 39 per cent have done so,' adding that between 20 per cent and 43 per cent of married women had tried it. The sodomy taboo is so great, Kinsey did not even have a question about it in his original survey in the Forties, and there is little information in Britain, though this should be rectified when the national Survey of Sexual Attitudes and Lifestyles reports later this year.

Britain actually has a law against sodomy. Between a consenting man and woman, it carries a maximum sentence of life imprisonment, the severest penalty among Western countries where it is a crime; in 1974, a High Court judge said it was 'as serious as committing manslaughter'. What is more, prosecutions have been brought: a lecturer raided by the police for drugs in the Seventies received an 18-month sentence when photographs were found of him buggering his girlfriend; a photographer was jailed for nine months for sodomy with a model. (It seems the women were not prosecuted.)

Yet in the Thirties, Dr Eustace Cheever found that 30 per cent of the married women he surveyed in Manchester had experienced anal intercourse. A 1972 readers' survey by Forum magazine found that 40 per cent had tried it. And an Elle magazine survey last year had positive replies from just under a quarter of its 1,000 respondents.

Recent academic work from Aids researchers tends to buttress these figures. A paper to the 1989 International Conference on Aids came up with a figure of about 20 per cent, and concluded that health workers needed to 'recognise the frequency of anal intercourse in heterosexuals'.

Sodomy, it has always been assumed, is something foreigners do more. 'The people of the South have also a congress in the anus,' says the Kama Sutra, rather dismissively. Englishman Wayland Young, in Eros Denied, written in the early part of this century, calls it 'the Italian manner'. V S Naipaul, fulminating outrageously against the Argentinians in May 1982, declared it was preferred by 'the macho' to straight sex. And Aldo Busi, a contemporary Italian writer, asserted in a recent book that Libyans, Croatians and Nigerians flock by the planeload to bugger obliging Moroccan women.

Contraception is the reason often given for the supposed prevalence of sodomy in Roman Catholic countries, although there is precious little evidence to support this.

Hostility towards the act remains tremendous, especially in Britain. 'Usually one partner - very sensibly in my opinion - decides he or she doesn't like it,' said a spokeswoman for Relate crisply. Alex Comfort in the New Joy Of Sex advises it is 'best avoided altogether'.

This is not altogether surprising: the Director of Public Prosecutions attempted to prosecute Forum for its postal questionnaire in 1972, arguing that the question 'Have you had anal sex?' contravened Post Office regulations. The same year, In Depth magazine was prosecuted for publishing a description of the act. (Both were acquitted).

Although there is a shortage of evidence, what there is tends towards the conclusion that heterosexual sodomy is an activity which a significant minority have at least tried.

Certainly, it would seem unwise to write off all danger of heterosexual Aids on the basis that sodomy is a freakish enterprise indulged in only by an underworld of dangerous, and probably bisexual, maniacs from sink estates.