Isettled back into the train seat and pulled a notebook out of my bag: something extraordinary had happened, and I needed to process it by writing it down. Speeding along the south coast, past Arundel Castle and on towards Bristol, I made notes about the night I’d spent near Brighton with a man I’d known for years, but seen again in a whole new context. About how delighted I felt, how hot, how incredibly free. My body, which had been pregnant in the Covid pandemic, given birth and then dragged itself through several house moves with a baby and a three-year-old, seemed to be renewed, on fire. My mind was blown, and my lips were bruised. I bought a beer and ate crisps. I texted friends, caught eyes with strangers: I wanted to talk to everyone about how I was feeling. Most of all, I wanted to tell my husband. For plenty of people, the idea that I could be so excited about a new sexual encounter, and at the same time in a truly committed marriage, doesn’t compute. But that’s the experience I’ve had for the last eight years, during which I’ve been married to my life partner, had two children, pursued career goals – and also seen other people. It hasn’t all been easy but, honestly, it hasn’t been fraught. Are we courting disaster? I don’t think so. Relationship boundaries are discussed more now that we’ve all begun to recognise how important they are, and how prone we are – as parents, friends, lovers, colleagues – to overstep them. One of the boundaries of a marriage, as most people understand it, is this: inside it, sexuality can be explored and expressed, but doing so outside destroys the pact a couple has made and, very likely, incinerates the love and trust contained within that promise. It’s kindness and honesty that keep a long relationship together, not the edict that our sexual selves only be expressed with one other person We believe this so strongly, often, that even thoughts of others feel dangerous; even a look across a room, held a second too long. For me, the openness we’ve brought into our relationship isn’t just about getting physical with other people. It’s about each being a supporter of the other person’s exploration and joy throughout their life. Acknowledging that we each experience a whole spectrum of desires, we let each other act on them in big ways and small: from me having a little crush on someone we play ultimate Frisbee with, to going on a spine-tingling date with a bewitching physiotherapist I met last month. In my experience, it’s kindness and honesty that keep a long relationship together, not the edict that our sexual selves only be expressed with one other person for the rest of our lives. I never planned to have an open marriage (or in fact to get married at all), and never had an open relationship before this. In my vague awareness of them, I thought they were tacky, probably foisted on one of the partners, and would likely lead to heartbreak. The day I married David came before we’d ever discussed a less conventional way to be life partners. It was one of the happiest of my life. So how did it happen? David and I are quite different (I’m an introvert and he’s an extrovert; I try far too hard to be cool, and he’s confidently daft), but we were also interested in some of the same things before we met, like dancing, theatre, and the kinds of exuberant festivals and parties where everyone dresses up and goes on strange and magical journeys. Exploring London nightlife before we met, we’d both been to Torture Garden – scarily named, but actually a big, popular night that encompasses a huge range of tastes, from people into fetish to those who are curious about alternative relationships, to those who mainly go for the music and social scene. In the first year of our marriage, we started talking about going together. We’d both assumed that world, which we’d only brushed up against before, was probably closed to us now; we were excited to discover it wasn’t. This discussion was organic, gradual and mutual, segueing from the language of fantasy into one of more concrete, real-world plans. It wasn’t driven by one person, and no one had to do any convincing. We didn’t know what it would feel like to experiment with other people, whether it would be the right step for us. We didn’t know whether we’d feel jealous. We went back to Torture Garden, together, and both found it extraordinary: the dress code extreme, and the atmosphere of freedom but also deep respect very different from anywhere we’d been to before. (As a woman who spent her teenage years and young adulthood going to “normal” clubs, constantly on edge about being touched or approached in ways that made me uncomfortable, these spaces and their focus on consent feel revelatory – and incredibly pleasant.) That night we chatted to people, admired others’ outfits and makeup. On the dancefloor we met a beautiful stranger, and all shared a kiss. We didn’t feel jealous. We felt thrilled, and very much together. There are an infinite number of ways to be in an open relationship. My experience is just one, our arrangements personal and evolving. It is hard to write about the specifics without everyone (me, you) finding it icky, but essentially David and I don’t just sleep with each other and, speaking for myself, I’m interested in intimacies of various kinds with people of all genders. The relationships we have with other people are sometimes fleeting, and sometimes go on for years, but we don’t think of anyone else as a “partner”. We never keep these interactions secret from each other; but nor does David ask to read all my texts. I feel beyond privileged to have someone I deeply love and with whom I have a fulfilling sex life, who is able to make delicious pasta dishes, sympathise when I have period pain, and co-parent our kids. Because, of course, we have kids. Two of them. The oldest is six and can read the blurbs on the back of my forthcoming novel– a fictional account of couples experimenting with non-monogamy – which is presenting a challenge. Eventually my kids might read this article. Even though I now know a lot of other couples in open relationships, I still think most people find it weird. We haven’t yet needed to talk to our children about our openness, or exactly how it works – though I’ve often thought about how those conversations might go, in the future. But in publishing my novel, I realised it was hard to avoid mentioning the life experience that drew me to that subject. What I’m doing, by writing pieces like this, feels like a coming out. It’s very easy compared to most people’s comings-out, in most of the world. But still, it’s public, exposing, and in some ways fraught. We are lucky to have wonderful families, but this is hard for some of the people we love the most, and that weighs on my heart. Some are very worried about us, thinking we and our children are likely to suffer, both because of the type of relationship we’re having, and because I’m writing and speaking about it publicly. Others disengage, perhaps finding it awkward or embarrassing. Still others are fascinated – a sentiment we often hear is, “I’d love to do that, but my partner would never consider it.” Most of my friends already know about our life, but I’m aware of all the people who didn’t – former colleagues, future bosses, exes – and now will. The discomfort is, hopefully, balanced out by how liberating it is to say your truth out loud and stand behind it. I hope my kids grow up understanding that. The blueprint we use for love and sex in a monogamous world suggests we do all our experimentation at the beginning, and then stop. Why? Having children intensifies a partnership. Before, you can ultimately make all your own choices. After, every decision you make – to work an extra hour, to go for a quick run – likely affects the other person, who will need to be bathing or feeding a child, tidying or reading stories or doing homework if you are not. If one of us wants to go out, of course, the other has to take care of the kids. If we both want to go out together, we need people we love and trust to look after them. In Mating in Captivity, the wonderful therapist Esther Perel points out that long-term relationships, as we have them today, are a particular kind of pressure cooker. We’ve moved on from the days where partners tended to specialise (one earning, the other cooking, for example), when each person had their own realm and set of social contacts. Today, we expect our partner to be a best friend, a satisfying intellectual interlocutor, often a co-parent, and to match us in earnings. We want them to do half the chores, be able to discuss the minutiae of a shared life – and to be our ideal lover. This intense intimacy, Perel notes, is in many ways the opposite of “the erotic”. Trying to find the otherness in one’s partner, she suggests, is important to maintaining a sense of attraction over years of familiarity. There are ways to achieve this otherness without opening up: it can happen when you go on holiday separately, or see your partner speak in public, or they get a new haircut. But in our relationship, we combat the routine nature of long-term love by seeing each other through the eyes of others. Watching him, chatty and flamboyant and thoughtful, and often dressed in zebra-print, I get to see the person others find hot. Meanwhile, I can put on huge boots, dance with splendid strangers, revel in the shape of my body – which isn’t always easy for busy, sometimes stressed-out mums. Knowing ourselves better sexually, we’re able to bring that self-awareness back into our own relationship. To return to boundaries, many people think open relationships have fewer of them. People in non-monogamous situations might argue they have more, clearer boundaries that are much more often discussed. This insight was made by my friend Joe in a long WhatsApp conversation about non-monogamy. Joe was interrogating my book’s tagline: Two Couples. No Boundaries. His words sliced through that juicy promise like a knife through a peach. Of course, there are boundaries in the book. In many ways, it’s about boundaries – and about crossing them. David and I haven’t felt the need to lay down hard rules for our relationship. So far, at least, we seem to understand each other and communicate quite well. We set aside times for the discussion of worries and annoyances, and usually do so out of the house, while walking. We also talk to each other about the more intense feelings that do, sometimes, come up: rejection or hurt, longing or confusion. Our relationship isn’t some kind of ideal template. We argue as much as many couples. We just don’t often argue about this. That doesn’t mean it’s always easy. When I stepped off the train after that incredible night away, I walked into several hard days. I found myself feeling really strong, but also spiky. The house was still a mess. Our son still didn’t like preschool. David wanted me to slot back into the exact groove I’d left. But I felt wild, in a good way, and didn’t want to fit back in. This refusal to be “the same” made David uncomfortable, and I wasn’t able to be kind enough about it – I was flowing with a new kind of strength, defiant, excited by the idea of breaking out of old, restrictive ways of thinking and being. Ultimately, one thing we discovered was that making one’s partner feel uncomfortable isn’t the end of the world, so long as you’re willing to take care of them afterwards, understand why, and maybe not do that thing again. The experience allowed us to better understand each other’s deepest desires and worries, in ways that keep resonating long after. We realised that there were things we both liked and wanted to try, that we didn’t necessarily have to do with each other; that exploring them with someone else might take the pressure off, and also give us more insight into who we are as individuals. If you feel attractive and loved, if you believe your partner won’t leave you, jealousy becomes less relevant We made some material changes too. That night away marked a moment of transition, both because it was a very powerful experience and because it made me feel powerful in myself, where I’d been feeling very powerless; in hindsight, I had postnatal depression, and this was one of the things that helped me out of that state. Newly empowered, I saw how things in our life could work better. We changed the way we divided up childcare, which had kept us tied to the house. The weeks that followed that trip include my happiest memories of our children at those ages. One day in particular stands out: the four of us dancing around the living room to Let It Go from Frozen, which I will for ever hear as an anthem for the kind of being-yourself liberation I felt that day. Here I stand, and here I’ll stay. I talk to my close friends about sex, but not, usually, in minute detail – it’s private, and a lot of us want to keep it that way. But that doesn’t equate, for me, to keeping it entirely under wraps in a hushed domestic space. I want to acknowledge that sexual energy can be wonderful, startling, generative, sometimes awesome in its power. Think now about the person you have wanted most in your whole life. Maybe you’ll notice some of these things. First, perhaps, a unique and wonderful feeling – being turned on is called that for a reason, because it can feel like a current of electricity has entered you: you’re ready, alert, seeing the world differently. Then you also might notice the sensation of not being allowed to think about that person. Maybe it’s not your partner. Maybe it’s your ex. It’s vastly interesting to me what we think is “allowed” when it comes to sex. I’m not talking about anything illegal or damaging here, just about the regular things people might fantasise about, but not think are OK. Kissing someone who doesn’t conform to the heteronormative script. Being tied up. There are some things that connect my sexual self throughout my life, like an unshakable obsession with Sean Bean (yes Sean, please do get in touch). There are others that have changed, ebbed and flowed. The sex I had in my teens (plenty, in retrospect, nice and non-traumatic) was very different from that of my 20s (still a bone of contention between myself and Cambridge University – intellectual hotbed, maybe, actual hot bed, no). My 30s were pretty great, with powerful sideswipes from pregnancy and breastfeeding. I’m tempted to say now is the best ever, with some caveats: the hormonal rollercoaster, which I’ve always ridden, is becoming more extreme. Like many girls brought up on a diet of Heartbreak High, Jane Austen and Keanu Reeves films, I always wanted to fall in love and imagined it being with one person. I went through plenty of pain losing people; and also the pain of a long-term single person craving a relationship, which I wish I’d spared myself. I was stunned and delighted when I did find that one person. But the blueprint we use for love and sex in a monogamous world suggests we do all our experimentation at the beginning, and then stop. We choose. We have to, because otherwise, what? Tackiness; incineration. I am not suggesting our way is an alternative blueprint. Maybe more that prints don’t need to be blue; or that we could let ourselves try mixed-media collage instead. People always ask me whether I get jealous. But why, really, do we feel jealous about the idea of our partner being attracted to someone else? Perhaps we believe we’ll compare unfavourably with that person, or we’re scared our partner will leave us. All our lives, we might have been told that “cheating” is reprehensible and immoral. Maybe we’ve been cheated on, and it was acutely painful. If you feel attractive and loved, if you believe your partner won’t leave you, and if you start to think differently about society’s insistence on monogamy, jealousy becomes less relevant. Maybe that sounds like a tall order and, indeed, I think I’m also lucky not to be “naturally” jealous. If I’d been cheated on in the past, I might feel differently. It’s worth noting here that the choices we make in our marriage feel very much like the opposite of cheating, not something adjacent to it. I should also point out that our “monogamish” relationship is very different, in its certainty that we are staying together no matter what, to other types of consensually non-monogamous relationships, and to polyamory. Not better; just different. It’s hard, once you have things like school places and mortgages to deal with, for life not to narrow. I love our access to other worlds, because the cute trans woman or the male-bodied god in a latex dress I meet on the dancefloor are very different from the people I meet on the school run. Or, and this is a thought that fills me with joy and hope, maybe they’re not. Maybe, having access to freer spaces allows me to see below the external, making me question my assumptions about who people are, and letting them be their most authentic selves. It’s really hard to be your most authentic self while doing crowd-control at a five-year-old’s birthday party, or pushing a crying baby through a cold park after a night of broken sleep. I’m not saying that being a dedicated parent, or enjoying a monogamous relationship, aren’t wonderful choices. I love being a parent, and I’ve loved monogamy. But right now – perhaps especially as a busy city mum with earning and admin, online food shops and bike maintenance and “normality” sometimes feeling like weights on my ability to feel lighthearted – this whole exploration is a pretty great contrast. Fiction likes to teach us about the consequences of infidelity: usually destruction of the relationship and often of the self. From Madame Bovary to Sex and the City: The Movie, most stories tell us, and have always told us, that infidelity is the unforgivable end point. But what if fancying other people is not unforgivable, and not the end? That was one of the sparks for my book and, I guess, remains one of the many sparks in my married life. Open Season by Cassie Werber is published by Trapeze at £20. To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.