I came to marriage by a circuitous route. As a radical feminist, I avoided it, certain it was for unintelligent girls who had no aspirations to travel or write books. I was never going to be ‘given away’ or called ‘Mrs’ Someone Else’s Surname. Working with abused women, I witnessed how marriage can do to good women what Chinese foot binding does to a healthy foot. Around me, I saw very few ‘happy marriages,’ between mindfully individuated people who were together because they deeply wanted to be. Even in people who seemed content enough with their spouses, I seldom saw that one ingredient I knew I could never live without: passion. So instead I determined I’d have lovers that came and went, the relationship equivalent of a sushi train, where you can pick what you feel like as it comes past. That way, I’d never get bored, and I’d never be stuck.

But then I grew up. I met a nice guy. We had kids (yes, out of wedlock). And twenty years later, I find myself in what seems to be a very stable and long-term marriage. My husband and I are good friends. He respects me. We are equals in the truest feminist sense of the word. He is non-violent, entirely supportive of my creative and economic development, respectful of my privacy and encouraging of my independence. But I’m starting to understand why good marriages flounder and why no-one is to blame. It’s got to do with a flaw we don’t often talk about in marriage – that love and passion struggle to co-exist.

The closer and more familiar my husband and I are with each other, the less sizzly we get. At times it’s like we’ve become the best room-mates and our raunchiness has puttered into abiding fondness. I don’t want to watch our sexual relationship fizzle out in bed- death, to become an erotic casualty of our familiarity and companionship. I want the person who knows me better than anyone else, to want me in that aching way we want someone we can’t have.

And if there’s any value to monogamy, there are important questions for us to grapple with. Like: is passion is sustainable long-term.? Does all this love, intimacy and equality make for good sex?

In her book Mating in Captivity, the sex therapist Esther Perel explains that love and passion’s agendas are often at loggerheads. Love brings security, respect and commitment, whereas passion invokes adventure, conflict and uncertainty, even domination and power. To reignite the erotic imagination, she says, we have to shelve ‘equality’ and enter the murky shadows of the erotic underworld.

My problem is that my entire identity has been shaped by feminism’s diet of egalitarianism, democracy and women’s rights. Have these starved me of the ingredients for long-term erotic subsistence? Will I have to abandon what I believe to discover something about myself I find confronting to admit?

My husband, bless him, wouldn’t think of taking an envelope out my drawer without asking my permission. But seriously, if he asks in that same considerate voice if I want to have sex tonight, he’ll get a gold medal for thoughtfulness, but a zero on the ‘bonk-me-now-baby-ometer.’

I’m intrigued by this conundrum. Why doesn’t respect translate into the erotic?

Perel says it’s because in love we merge with the other, and the erotic works through separation. We have to be able to see the ‘stranger’ in someone else to desire them. It’s why people have affairs – to keep the erotic charged in their lives. This has given me a new sympathy for adulterers, when I realize that to be truly erotically alive, we have to be imaginary adulterers, seducing our partners like Erica Jong’s nameless stranger in Flying High, to invoke their otherness, their inaccessibility.

So, I do an experiment one night. When he walks in the door in his business suit, I imagine my husband isn’t the person who strokes my hand when I have a headache or makes me a hot-water bottle when I have my period. No, he’s some strange businessman who’s wandered in and grabs me, pushing me up against the kitchen counter and talking the kind of dirty feminism taught me degrades women. And though the feminist in me fumes: Bingo, baby. Those floodgates open. Hallelujah. There is a monsoon.

I feel ashamed even admitting this, knowing that it’s neither PC nor how it should be. But feminist theory isn’t helping me have orgasms. Even if it’s true that having a man handle me roughly and speak to me like I’m a sex object is a function of my ‘false consciousness’ in which I’m ‘desiring what patriarchy has taught me to desire’, I don’t care. Right now, I want hot sex with my husband. And I’m looking for clues. And here’s one: the hottest sex we have is make-up sex after a nasty fight. When I like him least.

Another clue: once when a divorced friend confessed that my husband was ‘the sexiest man she knew,’ I pounced on him when he walked through the door.

Some of the yummiest sex of my life was with a man I didn’t want to date, wake up next to or even remain friends with. But to deny how turned on I was by our encounter would be disingenuous if I want to truly understand the shape and texture of my own erotic landscape.

If I can be honest with myself, what I desire doesn’t play by the rules of equality. There’s an excitement that comes from a secret place in the body which has no ideology. It’s a complex undisclosed sinew of myth, dream, fantasy, conditioning, upbringing, biology and mystery. What I imagine, in the sacred shadows of my erotic kingdom, is irrational, inexplicable, and a little scary. I don’t really want anyone to tie me up or make lewd comments about my body parts. In the safety of my marriage, I desire experiences that would shock me in real life. If I cannot speak this truth, then it will have to be repressed and tamed into the ever-after of erotically flat-lining marriages. Two thirds of which end up in divorce.

I used to believe good sex was courteous. But back then I was single and I wanted respect. Now I’m married and I want excitement. I want passion. I want it in the place I also come to for love, support and comfort. I’ve fought my political battles and now I want to fight for a passionate marriage. Feminism has made me a strong enough woman to face these strange and disquieting forces that tremble in the darkest forests of desire where the trickster antics of erotic imagination frolic freely.

I’ve protested against inequality all my life. I’ve marched, I’ve signed petitions, I’ve appeared on behalf of women’s organizations in constitutional courts, I’ve debated moralistic right-wingers who degrade women in the name of God and I’ve debated the pornographers who don’t give a damn about real women’s lives. And I will die fighting for the right of every woman to be treated as an equal in the boardroom, in the workplace, in her marriage – I want the safest and most generous world for my teenage daughter and every woman on this planet.

But behind my closed bedroom door, I reserve my rights to be someone’s skanky little slut.