As a young mother, I was haunted by the terror that one day a child of mine would die. It took root after my first son was born, and by the time I was pregnant with my second, it was unbearable. Superstitiously terrified that if I told anyone, it might come true, I kept it secret. But it was killing me. And then one day I cracked.

In another place and time, I might have gone to a village wise-woman, or a priest, or a shaman. Instead, I booked an appointment with a therapist.

“I’m going to lose a child,” I told him. “I don’t know which one. But one of them will die.”

When he said without hesitation, “We must take this seriously,” I was flooded with relief. Over the next few weeks, we explored where my conviction came from. The source was painful, and very private, and led to me making a small pilgrimage to lay a ghost – real or imagined – to rest. The strategy worked, and as my young boys grew up into healthy, active men, the old dread stayed firmly dormant.

And then on 6 February 2020, the phone call came. The boys’ father – by now my ex of 20 years – was crying. Immediately, the terror was back. He didn’t need to say a word. I just thought: which boy?

It was our younger son, Raphaël. A wildlife biologist, environmental activist, and a prominent member of Extinction Rebellion, he was awaiting trial for vandalising the Brazilian Embassy in London in protest at the trashing of the Amazon. My biggest fear had been that he’d go to jail. But now, at 25, and fitter and healthier than he’d ever been, he was dead. He’d been planning a documentary about anti-poaching units in South Africa, and was taking an intensive physical training course there in preparation. He’d collapsed on a group run – and they couldn’t save him.

His father, brother, then aged 30, and I were in three separate countries, thousands of miles away, and it took us more than two days to reach the place where he died, and speak to the paramedics who tried to save him. There is footage of him running, filmed just 10 minutes before he fell. He’s singing as he runs, and encouraging the others to sing, too. He’s happy, and in his element.

How can someone be so alive one minute, and then so dead?

It made no sense.

His body was on its way to a morgue an hour’s drive away. We had to see him. He lay on a trolley, wrapped in a plastic sheet, with his head and upper chest visible. It was only when I saw how stark his freckles were against the pallor of his skin that the full horror of it crashed in. I wanted to die, too. If there’d been an option that would had spared my loved ones pain, I’d have taken it in a heartbeat.

There were other imperatives. The pandemic was on its way. Hastily, we had him cremated, and took his ashes to London, where we held a big, wild, tearful memorial in celebration of his life. And then an eerie nothingness. The first phase was over.

Back home in Denmark, I knew that I was no longer myself. But who was I now? I simply didn’t know. The world had atomised.

And then came lockdown, a mass cocooning which in the madness of my grief seemed only fitting: my son was dead, so of course the whole world should come to a stop: how could it not?

The pandemic suited me and Raph’s stepfather. We didn’t want to interact with people. Every day, for nine months, I cried for Raph the hilarious baby, Raph the vocal, serious toddler, Raph the brilliant, eccentric boy, Raph the campaigning zoologist committed to saving wildlife. And Raph the dead body in the morgue.

I never relished my crying storms but I always felt better afterwards, grateful for the pressure change that followed, and perhaps instinctively aware that to resist the pain of my grief would only defer the process: that succumbing to the agony was – paradoxically – a vital part of my healing. If I didn’t fully acknowledge the pain, how could I ever metabolise it?

Around this time I came across a line by the Danish author Karen Blixen: “The cure for everything is salt water: sweat, tears, and the sea,” and I rolled it around in my head as I began swimming every morning in Copenhagen harbour. Summer changed to autumn and became winter and the sea was so cold that the thermometer was coated in a huge bulb of ice. And there, in the freezing water, I discovered another kind of release: the wild freedom of being a creature that existed nowhere but in the present moment. Sometimes Raphaël swam with me too: I could sense him underwater, his long hair streaming behind him, urging me on. If I could survive hypothermia, I told myself, I could survive the death of my son, and if I could survive the death of my son, I could survive hypothermia. That first winter, my harbour swims became the physical and spiritual proof of my capacity to endure the unthinkable. There was nothing masochistic about it: it was a vital, regenerative fix.

And I talked. I talked to him – as I still do – but more and more, I reached out to other parents who had also lost children and not only survived, but thrived. These mothers and fathers became my new role models, and they were generous with their wisdom. It’s said that when a mother elephant loses her child, the other elephants in the herd form a circle around her, to give her comfort. When my fellow bereaved joined my elephant circle, it felt complete.

But in the end, you can only do the work of grief alone. For me this meant searching for some kind of meaning – not in the loss of Raph’s life, which will never make sense to me, but in life beyond it. Words have always been my way of processing my thoughts and feelings, and over the months the books I read, and the words I wrote, became a way of looking around, and back, and forward. Forward was the hardest, because what was there to look forward to?

Alongside Raph’s birthday, there was a date I dreaded in particular: the anniversary of his death. The first year was brutal. But by the third year, I had learned to frame it not as a trauma trigger but as an opportunity to celebrate Raph as he deserved, and as he’d have wanted: with gratitude that he’d loved and been loved, that he’d lived his life to its the full capacity, and that he’d left a mark.

We think, when we’re in thrall to a deep emotion, that it will stay the same for ever. It doesn’t. But I realised that while the passage of time helped, it still needed my active assistance in the healing process. So now, when I get a sudden flashback to the morgue, I put a smile on Raph’s face and imagine him saying: “I didn’t die. I lived.” It’s not just wishful thinking, because it’s exactly what he would say. Knowing him so well, I have found that his thoughts and ideas have become my compass, and part of an ongoing conversation that feels vivid enough for me to know that although he’s physically gone, he’s still very much around.

The grief lies deep in me, and always will. But I have grown bigger around it. When I laughed for the first time after Raph died, I felt him cheering. He cheered again whenever I swam, or immersed myself in nature. He approved when I got a puppy, and when I began volunteering on a grief helpline. He rejoiced when his brother got married, and again when he became father to twin girls who have given the family more joy that we could ever have imagined. When I hold my granddaughters in my arms, I feel Raph’s arms around us all.

The world doesn’t stop when someone you love dies: it only pauses. But the pauses forge vital connections to our deepest selves, and as we emerge from them, changed, we find the world, and our relationship to it, has altered too.

Since Raphaël’s death, the ongoing destruction of wildlife habitats has been as devastating as he feared it would be. He spent his last months in a frenzy of activity, as if on some level he knew his days were numbered. A few months into my grief, I found a passage in his notebook that confirmed he did. It is a love letter to activism, and to a future worth fighting for – before and after his own death.

“I wonder how long it will take, or if we’ll ever get there. Perhaps we’ll reach this brave new world in a decade, perhaps we’ll still be moving towards that long after I’m dead,” he writes. “When the light leaves my eyes, and I pass on, do not weep for me, for I am not dead. All that I ever was and ever will be lies in the flame of passion that consumed me: the same flame that burns in all those who believe in what I believed. I’ll not be dead until my dream is. I’ll not fade away until my vision does. I’ll not be gone until all my hopes are.”

Raphaël will stay with me for as long as I live. But his legacy belongs to all of us.

The most likely cause of Raphaël Coleman’s death was undiagnosed arrhythmogenic right ventricular dysplasia, which caused the electrical signals of his heart to catastrophically misfire. For more information, visit Cardiac Risk in the Young at c-r-y.org.uk

Liz Jensen is a novelist and the author of the memoir, Your Wild and Precious Life: On Grief, Hope and Rebellion