When I started university in the late 1960s I thought I had the world at my feet. We all did. We were the children of the post-war boom, of swinging London and psychedelia. We were the ones who were going to change the world and it really seemed as if the transformation had begun, especially for women. In our first term, Sgt Pepper's Lonely Hearts Club Band was the album of the moment. We'd all pile into Lynn Barker's room in hall to absorb the full virtuosity of the Beatles on her stereo. We also tried to squeeze into Gary Arlott's room to squeal at Monty Python on his TV, but failed because girls weren't allowed in men's halls in the evenings. That outrage led to our first political sit-in. While other campuses were raging against the Vietnam war and the Kent State shootings in the US, we campaigned against the university's paternalistic residential strictures.

One girl, whose name was Sheila I think, ignored those constraints with glorious abandon. She was the university social secretary for a while, booking bands who today would not have got out of bed unless it was to perform at the O2 centre or Wembley, but in those days did the campus circuit just like everyone else. The Who played at a Saturday night disco, The Animals at another. Pink Floyd and Jeff Beck serenaded our May Ball. One night Sheila managed to smuggle into her room an entire band, The Move, plus their two roadies. Unfortunately, the warden of the hall had decided to take advantage of the balmy summer evening to hold a bridge party on her lawn. Disturbed by sounds of thudding and gasping, she flashed her torch into the shrubbery, only to confront the spectacle of a line of shaggy-haired rockers climbing out of Sheila's window, way after curfew.

What were they all doing in there? Who cared? Sex, to us, was more fun than fantasy. It had, we believed, been freed from guilt and squeamishness, thanks largely to the liberal availability of the contraceptive pill that the health centre would hand out like Smarties. That really was a liberation: no more reliance on the haphazard assurances of male partners; no more anxious visits to the loo to check and check for signs of blood. And if anything did go wrong, it wouldn't be a disaster, since David Steel's 1967 Abortion Act had at last done away with the terrors of knitting needles, baths of gin and seedy backstreet operations.

Even our clothes spoke of our new empowerment. The miniskirt announced not so much our flaunted sexuality as our equality. The look was more unisex than oversexed, in keeping with the androgynous mood of the day, exemplified by Twiggy. My first miniskirt was black and I wore it with a black and white check top and matching tights. Yes, tights - another liberation. Goodbye stockings and suspenders, along with those crippling roll-ons that our mothers winched us into in order to achieve perfectly flat stomachs to go with our pointy Playtex bras. Now we went free and unfettered.

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And then there were the trousers! Until the arrival of flares we'd had to do our best to customise our jeans by lying in the bath for hours in a vain attempt to shrink them into stylishness. Now, with flares, we could sew in printed fabrics, add sequins and butterflies or rainbows, suns and moons. And you didn't have to stick to jeans. For this was also the era of the trouser suit. Elegant, comfortable and practical it may have been, but male reactions to it really served as an early warning that far from being over and dusted, the battle of the sexes had only just begun.

Some restaurants banned women in trousers. So did many offices. The broadcaster Susannah Simon recalls being castigated one day in a Broadcasting House lift by a senior editor who told her off for wearing trousers to work. So, obligingly, she took them off, right in front of him.

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I met with similar outrage when I bought my own first trouser suit - a purple corduroy ensemble. My boyfriend hated it, especially as I had made the proud purchase to celebrate passing my driving test. Both gestures were interpreted by him as a direct assault on his masculinity. Or I suppose that's what he must have felt, since he left me soon afterwards for Frances, who always wore skirts.

I was obviously rather thick when it came to reading the signs that all was not quite as equal as I and my friends had assumed. When I look back now on my three years at the University of Reading it seems astonishing, for example, that I barely registered the fact that the entire English syllabus featured only one woman writer, George Eliot - granted an incidental mention as part of an introduction to the novel. I did try to sign up for the Jane Austen option but it was cancelled so I had to do the Pre-Raphaelites instead. One of our lecturers was the prodigious feminist thinker Juliet Mitchell, who was later to author a major reappraisal of Freud and who even then had risen to fame as the author of the feminist socialist polemic Women: The Longest Revolution. But what did she teach us? Erm, Dickens, actually.

At some point during my undergraduate years we were infiltrated by a bunch of postgraduate Trotskyists who struck me as dashing, romantic and intellectual. It was only after I'd fallen for one of them, a trade union activist who used to be a docker, that I discovered that seducing the middle-class girls was for these guys a new kind of conquest: it was a recruitment tactic, known by the inner circle as "fishy fishing". And it worked. I soon found myself attending meetings, memorising The Communist Manifesto, feeling guilty at the taunts that I was a bourgeois individualist because I liked reading Nova magazine, or that my essay on Ezra Pound's cantos exposed me as a treacherous revisionist.

It never occurred to me that, for all the talk of revolution and the new order, it was always the women who were stuck making the coffee and washing up afterwards. We never had much hand in composing the strike leaflets, the calls to action or the endless tracts, but we usually ended up having to type them and then reproduce them on an ancient Gestetner. It certainly didn't cross my mind that women were, even for the most radical of those Socialist Worker organisers, a bit of a joke. They endured us, patronised us, exploited us. And we didn't even notice.

And then came my eureka moment - the epiphany when everything fell into place. The Female Eunuch by Germaine Greer was published. And everything changed. For me, it was like reading the answers to a whole set of barely formulated puzzles. Why were we relegated to the back room at all those revolutionary meetings? Because, Greer explains, as long as women are seen as merely the means of production they will continue to be seized - and owned.

Was the Pill really such a liberation? Not if you consider that it meant pumping us with hormones every day, Greer warned, turning us into a generation of guinea pigs. Of course my English degree was devoted completely to the works of men. Women writers weren't thought to be on the same level as men. They're just literary female eunuchs. But why are we considered so inferior, so second-rate, so inadequate? Greer had the answer to that, too. "Women", she pronounced, "have very little idea of how much men hate them." And not only that, she seemed to imply, but we don't really recognise how much we disgust ourselves.

Not only was Greer bemoaning the stultifying, limited lives of housewives and mothers dependent on men. She was also throwing down the gauntlet to young women like me who thought we were free. You may consider yourself a fully realised human being, forging your own destiny, making your own choices, she seemed to be saying. Well, think again. You're as shackled and suppressed as anyone else. You, too, are a female eunuch.

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As evidence, she begins with the examination of our sexual organs, to show just how much they define us and make men loathe and fear us. "Part of the modesty about the female genitalia stems from actual distaste," Greer explains. "The worst name anyone can be called is cunt. The best thing a cunt can be is small and unobtrusive: the anxiety about the bigness of the penis is only equalled by anxiety about the smallness of the cunt. No woman wants to find out that she has a twat like a horse-collar; she hopes she is not sloppy or smelly, and obliterates all signs of her menstruation in the cause of decency."

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This angry diatribe is never more vituperative than in her treatment of menstruation. Greer reminds us of the many taboos surrounding the menstruating woman, and the religions that define her as unclean, unreliable, less than male, less than human. And, she warns, we are complicit in this disgust.

"Women still buy sanitary towels with enormous discretion, and carry their handbags to the loo when they need only to carry a napkin. They still recoil at the idea of intercourse during menstruation, and feel that the blood they shed is of a special kind, although perhaps not so special as was thought when it was the liquid presented to the devil in witches' loving cups. If you think you are emancipated, you might consider tasting your menstrual blood - if it makes you sick, you've a long way to go, baby."

It was an exhortation so spirited, so colourful, so funny that I have never forgotten it, nor the electrifying effect of reading a book that spoke to me so directly, so personally. The Female Eunuch was a call to action, a mustering of the troops. But it was also a graphic explanation of that fundamental tenet of women's liberation: the personal is the political. The book was published in the year when the seven demands of the movement were formulated: a comprehensive bid for equal opportunities. But unless we get rid of the idea that our breasts, our wombs, our curves, our vaginas are making us inferior, it proclaims, there can be no real change and no real equality. We must reclaim our bodies in order to make political claims for ourselves.

Biological differences between the sexes are tiny, Greer argues. Yet they are at the root of men's assumption of power over us. "Of forty-eight chromosomes only one is different: on this difference we base a complete separation of male and female, pretending as it were that all forty-eight were different. Frenchmen may well cry 'Vive la difference', for it is cultivated unceasingly in all aspects of life."

In this, Greer is echoing the mother of new-wave feminism, Simone de Beauvoir. "We are made, not born, a woman," she announces in The Second Sex - a book I discovered only after reading The Female Eunuch. This majestic work is usually the one cited by fellow feminists as their inspiration. For, in the wake of the wealth of literature produced in the past four decades, The Female Eunuch often seems to be downgraded, dismissed as too populist, insufficiently academic.

That must be in part because feminism has not fared well in the academy. The anger and passion that once fuelled us has been desiccated and deodorised, and sacrificed on the great altar of theory.

Disaffection with The Female Eunuch may also have something to do with Greer's rather uneven contributions in the intervening years - characterised by her appearance in Vanessa Engle's recent three-part television documentary, Women, when she came over as sour and unsisterly, in contrast to the joyful, sardonic warmth of that early work.

Nonetheless, The Female Eunuch deserves to be reclaimed. Witty, energetic and erudite, it has made an enormous contribution to the development of women. And reading it was my eureka moment - when I saw the feminist tide rising and triumphantly pulling the plug on the patriarchy. l

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Sally Feldman is dean of the School of Media, Arts and Design, University of Westminster.