The Outrun: My real life as an alcoholic, played out on the big screen

A common delusion among the mentally ill is to think they are being played on screen. But for me it is really happening, or I’m pretty sure it is. My memoir of returning to the Orkney islands and recovery from alcoholism has been adapted into a feature film.

Related: The Outrun review – Saoirse Ronan is remarkable in a sensitive recovery drama

Late at night, in bed with my laptop close to my face, I watch movie star Saoirse Ronan’s face reflected in her onscreen laptop, and I am looking into a weird mirror. The character she’s playing is based on me, and making this film has been like going through the looking glass.

One morning earlier in the year, I clicked a link and watched Saoirse at the farm where I grew up, in a boilersuit, with blue dye in her hair, rolling a cigarette. My toddler son pointed at the screen: “Mummy!” My essence had been recreated authentically enough to fool my child and to confuse and thrill me.

The next uncanny experience was watching “chemistry zooms” – audition tapes of Saoirse alongside other actors. Although she was still speaking in her Irish accent, rather than my light Scottish voice, the way she spoke and moved channelled me – my nervous delivery and expressive hands. I was freaked out but also immediately reassured by her talent. We had only met briefly online but she seemed to have conjured my manner through reading my words – their rhythm and spirit embodied.

Having the story of your life adapted for cinema is, of course, a rare experience but some of the effects it has had on me are, I began to see, amplifications and accelerations of more common processes of memory and sense of identity. Time and retelling bring distortions and realisations.

The project had a long development process. I first met dedicated powerhouse producer Sarah Brocklehurst eight years ago, before I met the father of my children. There were years of meetings when I thought nothing might happen. When the team came together, I had long conversations with supersmart German director Nora Fingscheidt – her in LA, me in Yorkshire – co-writing the screenplay.

We decided to name the main character Rona rather than Amy. This gave me some psychological distance and Rona became “she” in our conversations rather than “I”. Writing the screenplay, we allowed ourselves to step away from the facts and events of my life and introduce some fictional elements, while remaining true to the heart of the story and the realities of the time. There is nothing too unlikely or exaggerated, just scenes imagined for dramatic purposes. To make it easier for me, we didn’t include a brother character, although I am close to my real brother and he was a big part of my recovery.

We created a few fictional moments to solve a central problem of this adaptation: how to make visual what in the book is internal? How to show the healing power of nature? There’s a moment where Rona removes her headphones and lets the sounds of her natural surroundings come in. There’s a scene where, hit by cravings, she runs off a ferry before it departs. Neither of these things actually happened to me but the emotions and decisions they convey did. Nora was extremely clever at taking elements of the book and our conversations and combining them in new, powerful ways.

When writing, mostly I was detached, thinking only of how to make a good piece of art, using my experiences as material. Occasionally a memory – lines based on a drunken fight I had with a boyfriend 15 years ago – would get me and a real feeling returned: that of knowing I had nowhere to turn but sobriety.

There was a point in the film’s development where things seemed to happen fast and suddenly the producers were securing investments, signing contracts, casting actors. Meanwhile, I was buying apples at the market and getting my sons to put their shoes on. A designer made a mood board of the 2009-ish east London party scene: my life as a costume drama.

I wrote the book alone at the kitchen table of a cottage on the tiny island of Papay, and – astonishingly – location managers and directors of photography were searching Orkney for the right farmhouse and fields, consulting boatmen and ferry timetables, asking the RSPB for advice on how to film an actor being dive-bombed by Arctic terns. Prop designers recreated a drawing described in the book and designed special beer bottles.

They decided the best location to use was the actual house on Papay, the actual kitchen table. The film’s method settled between fact and fiction, between documentary and drama. Nora used some real people: farmers, islanders and actors who had been through rehab, who workshopped scenes with a loose script. The results are fresh and authentic.

They filmed in Dad’s sheep shed and caravan on the piece of land called the Outrun. They were the real locations but not the real Dad, or the real Amy. Saoirse, an experienced actor, had never played a real-life person who was still alive. It was strange for both of us and we were cautious with each other. For the part, Saoirse learned to lamb a sheep and build a drystone dyke. She froze herself in the Atlantic and learned about seaweed. She became not Lady Bird nor Jo March nor Mary Queen of Scots, not even Amy Liptrot, but Rona. I began to see Rona as a collaboration between me, Nora and Saoirse: a new entity.

During the summer of shooting, my mind was blown by the daily call sheets – lists of the personnel, vehicles, movements and catering needed each day. Late each night I was sent the rushes, all the footage they had filmed. I had 46 mornings of waking up to an intense link and, when I clicked it, a new reality rushed in. As soon as the scenes were filmed, they were no longer how they are in my memory or readers’ imaginations but a new physical manifestation.

I visited the set a handful of times and loitered among all the vehicles, cables, lights, people in black puffer jackets and hi-vis vests with radios, carrying equipment. Observing the female-led team at work, each focused on their task yet working as a group, was highly impressive. Everyone was capable and positive, even at the end of a long day.

I had a sense of responsibility for the crew dedicating a summer of hard work and also for how the filming was received at home in Orkney. I started smoking cigarettes and drinking Coca-Cola like I did 10 years ago, reverting to the Amy of the book. My jaw was clenched. I started dreaming about the film every night: that the crew was in my bedroom, that I accidentally destroyed reels of film.

While most of it was happening, however, I was at home in Yorkshire doing the school run, making cheesy pasta, hanging laundry … while in London, then Edinburgh, then Orkney, a big team followed in my footsteps of a decade ago. I wasn’t there when the crew, using a helicopter, recreated the prologue of the book, the day of my birth.

A crew of around 30 filmed on Papay for three weeks, increasing the population by half and filling every spare bed on the island in a culture clash described by Papay resident Jim Hewitson as “Beverly Hills came briefly to the isle of Celtic monks”. Islanders were employed as runners and extras. I travelled to Papay for the last days of the shoot and watched from a distance, on the handheld screens of the crew, as Rona walked repeatedly up the beach gathering driftwood, recreating my psychological state of a decade ago. As I walked away, I had a weird sense I was doing an impression of Saoirse doing an impression of me. I was hyper self-conscious of my face and mannerisms.

After watching a few scenes of this mirror world, I decided that Rona is a better version of me than I am: she’s giving a more convincing performance, her emotions more authentic, motivations more clearly defined, experiences more deeply felt. I was never as committed to the role.

I start to get confused and feel scenes from the film, more present and vivid than my memories, are actually things that happened. I don’t recall the face of the doctor who referred me to rehab 12 years ago, but I can clearly picture the actor playing the part. Did I run off the ferry like that? The film starts to replace the real events in my memory.

Back home, I look in the mirror with some disappointment: I’m 10 years older, not a film star.

As a diarist, I use my diary as a memory, letting things I haven’t written fall away. As a former drunk, I am also used to partial recollection, experiences that never formed memories. I am confronted by Nora’s strong directorial decision to stay with some of the drunken episodes, to let them play out in awful detail. It is difficult to watch and necessarily so. The Outrun is at its heart a story of recovery – I am well beyond this time so it is distant for me. To my relief, the film team was more involved in my alcoholism than I now am.

The editing process was fascinating. I saw how small decisions can do a lot to change emphasis and signpost meaning. A couple of parts from the book, which I saw as particularly cinematic and suitable for a film adaptation, did not make the edit: the part where I ran naked around the Ring of Brodgar and the part where I found a washed-up bottle of vodka. We tried them out but, despite being real events, they were almost too unbelievable and cheesy.

When I step back I think, wow, it really happened. It’s truly the dream – although a dream that is not uncomplicated. To have the most dramatic scenes from my life play out one after the other is intense. For reasons of plot and drama, the film concentrates on the family story and sharing these truths comes at an emotional cost. But the film, based on my personal story, has made these things into art, something bigger than me: a story of the power of place and community, of confronting your past and the elements that made you, and the possibility of change.One of the themes of The Outrun is the link between mental illness and addiction and the desire to reach for extremes. This film-making process has been another example of these extremes. I am amplified, cinematic, extra-real.

I appear in the film, a writer’s cameo, as one of a group of swimmers. Rona is unwilling to get into the water, but I am out there in the sea, in the future. The film is a representation – an adaptation – of a particular time, but my real life has continued, continues, and I am finding a way to maintain my own sense of identity among it all, a grateful recovering alcoholic, a decade and 500 miles away. I’m letting go and floating between the co-existing layers, knowing I am real and alive and swimming out ahead.

• The Outrun by Amy Liptrot (Canongate Books, £10.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.