WHEN Tamsin Calidas stepped aboard a ferry bound for the Hebridean island that would become her new home, it was with hope for a fresh beginning, one far from the tumultuous events and near-death experience she had faced in the city streets being left behind.

Only a few weeks earlier, she and her husband Rab had spotted a newspaper advert for a derelict, rundown croft. It seemed like the perfect place to make their own and one day raise a family.

Instead, life would be torn apart at the seams – loss, grief, injury, betrayal, abandonment, isolation – as their pipe dream collided with brutal reality amid the wild, rugged landscapes.

Yet, it is also a story of courage and resilience, discovering unexpected beauty in the midst of anguish and finding ways to heal using the perilous terrain that almost broke her.

Calidas has written a powerful memoir, I Am An Island, about her experiences (the island itself is unnamed in the book, an anonymity requested by her publishers to protect the author's exact location and the privacy of those who live in the surrounding community).

When we speak on a late April morning, Calidas has the nerves of many first-time authors, mixed in with trepidation that her words should not be taken the wrong way or framed out of context.

It isn't meant to be a polemic on island life, she asserts, emphasising that the book is not written from a place of anger or blame. Rather, insists Calidas, it has been borne from a deep love and should be viewed as "grace notes of a much deeper experience that was lived".

First, let's rewind to 2004. Calidas was living in London. In the years previously, she had enjoyed a high-flying career as a photographer, working in broadcasting, publishing and advertising.

Then came a seismic event that upended her world. A black cab jumped a red light and collided at full pelt with the taxi Calidas was travelling in. She suffered serious injuries, including a smashed sacrum, fractured coccyx and severely prolapsed lumbar spine.

During the intensive rehabilitation that followed, Calidas took stock and changed paths. She met and fell in love with Rab. They moved to a bigger house in a nearby area, drawn by the strong sense of community, and it was there that Calidas dreamed of one day having children.

"It was a family neighbourhood and felt very safe when we first went there, but then suddenly everything changed overnight," she recalls. "As I say: 'London neighbourhoods are transient. They can shift as quickly as the low skies gusting overhead.'"

Things became dark and feral. Spray-painted graffiti was daubed on buildings, windows were broken, a neighbour was mugged. The final straw came when someone stole Calidas's keys and returned to break in to her home during the dead of night.

London no longer felt safe. The couple embarked upon a house-hunting expedition in the north-west of Scotland. "I originally didn't want an island because it felt one extra degree of difficulty that we would need to navigate," says Calidas. "Then, suddenly, here was this amazing advert.

"It was total random chance that we saw it in the paper that day. It had everything – both for and against it. It was the one thing we said we would never do but was offering us so much potential."

Reflecting now, Calidas is able to recognise the deeper undercurrents at play when she fell in love with the dilapidated croft which, lying empty for years, had no electricity or running water.

"I suppose it is quite Jungian in its philosophy," she muses. "We seek our own crisis to find our healing. I was drawn, in whatever way, to that aura of abandonment and I felt a connection instantly. I felt something inside calling me and something inside me lift.

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"In a sense, there was a feeling of recognition and that, in itself, fired up my desire to love it and make it a home. And through that act of love, to claim it and to hopefully then gift it with our own children and a family to hold within its walls."

Six weeks later, the couple packed up their belongings and headed north. There was an inauspicious hitch when the tailgate of the removal lorry was too low to board the antiquated boat. As her husband remained on the mainland seeking alternative carriage, Calidas sailed for the island alone.

It would be an early, ominous portent of what was to come. Throwing themselves into crofting life, however, things felt promising initially. An elderly couple visited bearing shortbread and tablet, while another neighbour left an old wooden chest of drawers in the yard as a housewarming gift.

Not everyone was welcoming. There were signs of hostility, sometimes open, others bubbling beneath the surface. "Each pocket of soil is as jealously guarded as any close kinship," she writes in I Am An Island. "Kinship and soil are fiercely defended territories. To name it, you have to claim it.

"Yet, for all your effort, you never deserve it. Belonging is at the behest and tolerance of others jealously guarding their own right to the soil. The history of this croft matters. Its loss is a palpable grief to some and a source of enmity to others."

Calidas recounts hearing the word "incomers" when they first visited to view the croft. "It felt like a piece of litter that had been dropped on the ground," she says. "But I hoped with time passing that would change in its tone and we would connect.

"This was a very different time, remember, that I'm writing about – over 16 years ago. This island was less densely populated then, and I think there was a real sense of loss.

"It must have been difficult for some. We were young – in our early thirties – and walking in to buy a place that perhaps some may have wished for their own children. When we arrived, it was quite an elderly population. Much of our peer group was away working or living elsewhere.

"Whenever you have a finite stretch of land and the terrain is restrictive, every blade of grass does count. I did say sometimes I wondered if we would ever be forgiven for buying our piece of land."

Together, she and Rab began the necessary toil – a mix of physical, hard graft and psychologically taxing labour – to revive the ailing bones of the cottage and work the land to make it stockproof.

That autumn, they bought sheep, a mixture of Cheviots and cross mules from the older Black Face sired by Blue Leicester, for its strong bones and fine wool. Then, in spring, came the first taste of lambing, described by Calidas as "scarily, viscerally real".

This arrival of new lives was a stark reminder of her own yearning. When Calidas was unable to become pregnant, the couple turned to IVF. It provided a fleeting glimmer of hope which, when unsuccessful, brought fresh emotional tumult.

Calidas noticed something shift in her husband. There was an infidelity. A quiet, brooding anger became increasingly more volatile. The couple's relationship, already frayed, tore apart completely.

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Her husband left and returned to London. Calidas was alone. The timing could not have been worse: she had two broken hands, injured in separate accidents. The constant, debilitating pain made tending the land and animals a nigh-on impossible task.

Yet, Calidas did not give up. She found ways to adapt. When collecting kindling in the woods, she figured out a way to drag it back to the cottage using a rope tied around her waist. When there was no workaround, she would simply grit her teeth and attempt to push through the searing agony.

There are countless raw, visceral moments, such as when she talks about taking a sharp blade to remove the skin from a dead lamb before tying it to another newborn lamb, allowing the survivor to be twinned with the ewe.

To hear her speak, it's remarkable to think that Calidas hasn't been doing it all her life. Much, she says, was learned on the job. "We had zero experience. I have a natural touch, I suppose, with animals and plants. It is something I have always had.

"At the beginning, we split the chores. When Rab left it was a hard, fast task of learning how to do things. Thank goodness for all the books I have here because the internet isn't always reliable. You have to learn very quickly when there is a life at stake."

Some islanders struggled to understand why, when Rab departed, Calidas didn't leave too. One former friend angrily confronted her with the accusation: "You've no right staying on now he's away."

The truth was she had little choice. "On a logistical level I couldn't leave," says Calidas. "The house wasn't finished – some bits hadn't even been started – and it was in a total state of disrepair. There was no regulatory certificate to enable it to be sold and I was up to my neck in debt."

Looking back, Calidas must surely be impressed with her own tenacity? "I'm incredulous now," she admits. "I was surviving and the strength that comes through that inner will just to hold on and cope, pushes those tolerance levels beyond what normally you might think you are able to do.

"As bigger and bigger experiences kept throwing themselves at me, coupled with the sense of being alone, the intensity was amplified as I tried to hold everything together."

One of her greatest joys was meeting Cristall, an older woman who lived on the island. The two women connected after Calidas pinned an ad on the post office noticeboard offering her gardening services for hire.

They forged a close-knit bond and friendship, with Cristall becoming a mother figure and a shoulder to lean on as Calidas's marriage broke down. When Cristall's husband Anthony became progressively more ill with terminal pancreatic cancer, he asked Calidas to look after his wife when he was gone.

Later, the women made their own pact: neither would leave the island without the other. Calidas writes of this moment: "I feel so happy it almost hurts." The next morning, she watched from her garden as Cristall drove past with a cheery wave, off to catch the ferry and visit relatives on the mainland.

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The pair had made plans to meet that afternoon for tea at a harbour hotel. Calidas waited. But Cristall never arrived. Word filtered through about an accident further along the road, two cars in a collision. Cristall was cut from the wreckage. She did not survive.

The grief hit like a tsunami. "She was everything to me – she is still everything to me," says Calidas. "When I made that promise it was such an immense conversation because it was probably the only time in my life that I have really said all that I've wanted to say, when it needed to be said.

"The next day she was killed in a head-on car crash and that broke something inside of me. I buried myself after that. It was the start of the decline."

She chronicles the downward spiral that followed with unflinching honesty. Nature came to the fore in spellbinding manner and one of the ways that Calidas healed herself was through wild swimming. "The sea unpicks that lock," she writes. "It releases everything that is held silent or bound inside."

When she first immersed herself in the icy waves, however, it was because she felt unable to go on. This was a pivotal moment. Instead of wanting life to end, Calidas felt revitalised.

"With that immense connection I already had with the landscape, there was a feeling of being safe and held," she says. "It was a totally shattering experience but one that turned my life around.

"When you hit rock bottom, it is that thin line between breath or no breath. Being in the water kickstarted my system. I struggled and held on to my breath.

"Fear is a theme that rides through the whole book – it is incandescent, it can be blinding, it can steal your voice and can almost stop your heart. And yet, you still have to take that next breath in order to keep moving."

Calidas continues to swim daily in the sea ("It gives so much courage, focus and perspective. Living alone it is something that gives me a deep feeling of kinship") and when struggling to put pen to paper about her feelings of losing Cristall, she knew instantly what would help.

"I went back to her home and was in the water there and able to express what I needed to express. Afterwards I had a very difficult night where it felt like I was wrestling with all of these deeper emotions and fears. I sat down the next day and that's when the chapter came all on its own."

Earlier she had talked about forgiveness. Does Calidas feel that is finally forthcoming from those who may, at one time, have resented her arrival on the island? "I think I have earned it," she says. "The struggle – it's a harder life up here and out here.

"When people put their blood, sweat and tears into their lives and work, and show themselves willing to stick it out, to take the rough and the smooth, I think an acceptance comes. With the years passing, you are no longer the newest face on the land. I would hope that continues with time."

Her strong maternal instinct is woven throughout the book, from hand-rearing orphaned lambs to caring for an injured young hooded crow. Not to forget her fierce love for Maude, the collie she raised from a pup who remains her constant companion.

The heartache of infertility is, even today, a subject that many people find difficult to talk about. Calidas gives a voice to those similarly affected. Did she find it cathartic to revisit that pain – or was it akin to pulling the scab off an old wound?

"I would say it is both and that's a good analogy. Because for something to heal, you have to pull that scab off to get right back to the raw material, scrape that away and start to let it heal."

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All her regrets are laid bare. What is Calidas most proud of? "Being here," she says. "It almost feels like I have come full circle. To have been able to not only survive, but now to start to thrive is an amazing place to be.

"There is a lovely bit in the book where I say: 'It is always during the notion of transit that your heart opens and all of your dreaming begins.' It's a great feeling to know I have started to dream again. It will be interesting to see how life opens with that."

I Am An Island by Tamsin Calidas, published by Doubleday, will be released on Kindle and as an audiobook on Thursday. It is available to pre-order in hardback