I’m four and I’m pretending to be dead. I’ve been lying here behind the sofa, and I’m hoping I’ll be missed, but more than that I’m hoping it will make a story. The story of the games I like to play, and how I profess to remember my past lives. It is 1967, a few months before we set off for Morocco – my mother, my sister Bella and I – travelling overland by van, taking the ferry from Algeciras to Tangier, breaking down on the road to Marrakech. From then on everything becomes a story. The camel festival we visit, the path into the hills so steep that Bella and I are packed into saddlebags while the donkeys’ hooves skitter and slip. I can’t remember later whether it is a camel that is sacrificed when we reach the top, or a chicken. But either way I keep the description of the chicken to myself, running in circles, blood spouting from its headless neck.

For all the decades since, I’ve been the family chronicler, as much in my novels as in our lives. I’ve kept the few possessions from those years in Morocco. The kaftans we bought in the souk when we arrived, the corduroy patch that I unpicked from a pair of too small trousers, embroidered with a flower by a boyfriend of my mother. “Are you my Daddy?” I’d asked him, as I’d asked others, not because I thought he was, but because I’d read about another little girl asking the same question in a book. I can still see the look of consternation on the boyfriends’ faces, hear my mother’s embarrassed laugh.

I had a treasure box in which I kept a choker, coins with Arabic stars, lengths of braid, and when, aged six, we returned to England and I started school, I saw the minutes set aside each day for “news” as an opportunity to expound. To tell my classmates how I saw a mirage in the desert, found amethyst in a seam of rock as we hitchhiked through the Atlas mountains, became lost on the beach at Agadir, until I was nicknamed “In Morocco …” and I learned to stay quiet. But the stories remained, coalescing, condensing, until in my mid-20s, on a break from the acting career I’d chosen for myself, I began to write them down. At first they were nothing more than anecdotes, but slowly, painstakingly, I forced myself inside them until I found the voice of the child I’d been, the scent of the alleyways, the heat of the baked earth, the fear and exhilaration, the freedom of our lives. “Hideous kinky,” my sister and I would murmur to each other when events became too strange or too confusing, and so, when it was finished, Hideous Kinky was what I named my first novel.

As an actor I’d immersed myself in Stanislavsky, consoling myself that spells of heartbreak could be repurposed “for my art”. As a writer, I found that everything and anything was useful, and as I mined my life, digging deeper, unearthing half-forgotten truths, I wondered about the splinter of ice that Graham Greene so famously alluded to, and whether it really does lurk in every writer’s heart. Is having a writer in the family the death of the family?

I wrote my first novel in innocent naivety. The second was finished in a burst of exhilaration before the first was published, but for my third – nerves shattered, my mother reeling (who wants their five-year-old to remember every experiment in parenting and write it down?) – I turned to history. Berlin during the first world war had never been my subject, but I had the seeds of a story about my German Jewish grandmother gleaned from my father, Lucian Freud, during long hours of sitting for a painting, and much as I struggled, pre-internet, with the research, at least (if I ever managed to finish it) there was no one left alive to be furious or upset. Four exhausting years later I published Summer at Gaglow, and almost immediately, as a reward, I plunged back into my own life, to rake over the experience of living in a step-family, as I myself had done from the age of eight to 14. That’s when I discovered I’d become a different writer. I’d gained the confidence to invent, when often it had seemed no invention was needed – what, in actuality, could be more surprising than the truth? I had taught myself the art of camouflage, and by doing so had created a level of protection for everyone involved.

In the books that followed I was free. That’s not to say I didn’t sometimes agonise, but I’d learned to pick and choose, research, obscure, allow my characters to spread their wings and fly. So it is with trepidation that I have returned to the central relationships at the heart of my first novel. My Sister and Other Lovers draws on the themes that shaped my writing – family, loyalty, division – the completion of which has coincided with the new storytelling career of my fashion designer sister, Bella, who has been publishing a weekly column on Instagram, Sunday Stories.

How strange, over this last year, to read my sister’s interpretation of events. Free from the wiles of fiction, her voice rings out, clear and clean, and I am tempted to respond, as she must have been doing for years: “That’s not what it was like!”

The Polish poet Czesław Miłosz is quoted as saying: “When a writer is born into a family, that family is finished.” So what happens when there are two writers in the family – I won’t even mention here my literary half-siblings – and is it fact, or fiction, that comes closer to the truth? Screenwriter and memoirist Nora Ephron once declared that all writers are cannibals, and her own mother, a writer herself, is known to have insisted that “everything is copy” – something Ephron proved with Heartburn, a blisteringly funny and painful account of the breakdown of her marriage. But even she must have wrangled with the dilemma: What exactly is allowed? What remains off limits? There’s no doubt I’ve been eyed by friends who’ve read my stories. “Gosh,” they’ve gulped. “You do have a good memory.” Then, of course, there are those friends with whom I’ve lost touch.

For the last 15 years I’ve been running a creative writing group, and the experience has taught me that what makes it difficult for people to commit to the novels they long to write is the burning question: What will my mother say? It doesn’t matter whether this mother is alive or dead. Secrets, and the shame of them, have a way of stopping people in their tracks. However hard I encourage them to write – to edit, abandon, disguise the work later – fear acts like a bindweed. No wonder writers need that splinter of glass. Julian Barnes has said that while working on his first novel he had to pretend his entire family was dead. But what has surprised me more is the mistrust of anything considered to be true. If a piece of work is semi-autobiographical my students often tend to give it less value. That’s brilliant, I might respond, only to be met with a dismissive shrug: it’s virtually all true. This is a phrase I’ve been tempted to ban from the class. What matters, I try to impress upon them, is that the story is alive. And which story, once repeated, is ever actually all true? Is this because for years so many novels by women were branded as “domestic”, categorised as aga sagas, chick lit, while the angry young men of the 1950s and60s created kitchen sink drama unimpeded? More recently there’s been a wave of Autofiction which has risen above this prejudice, by Maggie Nelson, Annie Ernaux, and the ‘living autobiographies’ of Deborah Levy. Which brings me back to my sister’s Sunday Stories and whether it is fact or fiction that gets closer to the truth. Could I have told my own stories as memoir? Would I have had the courage?

For me fiction is the frame I need to tell the stories I’ve been turning over all my life, the writing of which has freed and saved me. As I dig I can feel the splinter of glass pressing so hard it threatens to draw blood, but even as I worry for those I love, who inadvertently I may have hurt, I tell myself: it’s fiction. And I remind myself of my father’s liberating words after reading an early novel in which a character (just possibly) based on him appears. “For a moment I did think it was me, then I realised: I don’t wear a watch.”