Two decades ago a girlfriend of mine told me how she had been raped, though she didn't use that word.

Two decades ago a girlfriend of mine told me how she had been raped, though she didn't use that word. A few years earlier, as a 16-year-old doing holiday catering work, she had first been leered at by her supervisor (a man of 40-odd), then groped and finally, after a fortnight or so, pushed into a stockroom and forced to have intercourse. She never went back and never complained. A couple of years later, another girlfriend confided a similar story. They were both quite fatalistic about their experiences; enough to prove that widespread rape and sexual harassment were no inventions of hyperbolic feminists.

It's different for boys. Henry Fielding once lamented that men could not be taken by force by women, and it's true that when we have sex against our will we tend to succumb more out of politeness than fear (this even happened to me when I was younger, and I recovered very quickly).

So it's small wonder that one of the most successful movements of the Seventies and Eighties was the campaign by many women to recognise the abuse of male sexual power against women. Unsurprising, too, that with educated women to the fore, universities developed some of the most stringent policies designed to prevent the sexual exploitation of (predominantly) younger women by (invariably) older men.

Yet human beings are always more complicated than policies. Every act of teaching, a friend of mine asserts, is a seduction of a kind: it involves the teacher attempting to persuade the pupil to go somewhere that they otherwise would not go. When I was a student at Manchester, I somehow missed the sexual energy that was supposedly discharging itself like invisible lightning in seminars and lectures. But then, I was so dense at that age that the lecturer and the forward gal from Cheadle Hulme could have been copulating on the floor, and I still would have been arguing about the class basis of the Peasants' Revolt. I hadn't read The History Man.

And if modern history offers a minor stimulant, creative writing courses ­ by many accounts ­ are a direct injection of emotion and sexuality into the bloodstream. Here people bare themselves, strip naked, in front of tutors and their fellows, desperate for validation. What's more, these courses are shorter, more intense; the people on them are older. They are more adult in every way.

The most famous creative writing course in Britain is the one at the University of East Anglia in Norwich, founded by the late Malcolm Bradbury ­ author (as it happens) of The History Man. For the past five years or so, Bradbury's chair has been occupied by the Poet Laureate, Andrew Motion. In addition to being a fine poet (as far as I can tell), Motion is also damnably handsome and very charismatic. So, steamy course, sexy man.

Last autumn, the 36-year-old writer Laura Fish, single mother of a five-year-old and author of a critically acclaimed first novel, Flights of Black Swans, enrolled on the one-year UEA course. Within just a few weeks, she complained to the university authorities that Andrew Motion had sexually harassed her. He had apparently sent her e-mails of a personal nature, had kissed her and had visited her flat (which is on campus).

On 8 December, she revealed to journalists this week, the dean of English and American studies, Jon Cook (a Fish, a Motion and a Cook ­ I can hardly believe my luck) wrote to her, stressing how seriously the university took her allegations. The dean stated that he would, from then on, sit in on any tutorials involving tutor and student. "I will warn [Motion]", wrote Cook, "that he risks dismissal if he behaves towards others as he has behaved towards you. He will be told emphatically that no repetition of what happened to you can be tolerated." A month later Ms Fish declared herself satisfied with the university's response. Now, however, she is demanding a formal investigation into Motion's actions.

Motion says: "I have reluctantly been obliged to make a complaint to the university authorities about a mature student on the creative writing MA course, in which I have accused her of harassing me and of slandering me to the press and elsewhere." Motion's wife admits that her husband may have let Fish become too close, but described the allegation of sexual harassment as "complete fantasy".

I stress that I have no idea of the truth of these allegations, nor of Mr Motion's subsequent counter-accusations. Nor can the Sunday newspaper that speciously linked the Motion and Greer kidnap cases last weekend have any better idea than I do. Even so, there is something disproportionate about this whole business, and in particular the university's reaction to events.

A kiss, a few e-mails and a home visit may constitute, depending on context, inappropriate and unwise behaviour on the part of a tutor. But only a panicky legalism can transform them into a sacking issue. Regulations are a blunt instrument when dealing with largely consensual behaviour between two mature adults, even when one of them is a student.

To put this as bluntly as possible, Motion and Fish, grown-up writers with children, should have been able to sort this out between them without recourse to the institution. A 36-year-old woman should not need the protection of a dean from unthreatening e-mails.

Am I saying that age or maturity should accord a person less protection? I am certainly saying that circumstances alter cases. In the conventional model of tutor/student relationships, one is an all-powerful semi-deity twice the age of his devotee and in charge for three years. But these days, when there are so many mature students and women teachers, that model seems less useful. Suppose, for example, the student had been 48 and the tutor 26? Would the dean's letter have made much sense? If there has been no attempt to force a sexual relationship, no question of "sex for diplomas", why would a dean need to interpose his office between these two middle-aged persons?

One answer could be: back-covering. As an American university warned its staff: "In the eyes of the law, when an institution knows or should have known about a sexual harassment problem, the institution can be legally liable." And a consensual relationship may be no defence, because "in the future, should the relationship fail, problems may arise. Consent at an earlier period does not preclude a charge of sexual harassment later, if the individuals were in both a supervisor/supervisee and a romantic relationship."

In other words, the university could be sued if someone changed their mind. So all relationships between staff and students, even if they don't involve what the rest of us understand to be sex as such, are to be treated with equal severity. The message to tutors is: do nothing, don't get involved, don't visit, don't flirt, keep the door open and your hands off your keyboard, treat every student as a potential complaint on legs. And I do not see why a British university would want to be any less careful than an American one.

I may be wrong, but it seems to me that we should be more adult about this. Things happen between grown people that are difficult to legislate for and hard for outsiders to comprehend. Our lives are tangled and infinitely negotiated. Unless there is a real abuse of power and real villainy, the intervention and legislation of deans serves rather to infantilise relationships than to improve them. Institutional protection is something that we should aspire to do without, except in extremis. Otherwise we all have to behave like kids.

This is my distinction in the end. My girlfriend who was harassed and vilely abused needed and deserved help. I never did.

David.Aaronovitch@btinternet.com