The pain was getting worse. The tips of my son Deryn’s fingers were hard and black from a superbug infection. His nails were peeling away and any remaining live flesh was covered in weeping sores.

Every day, he begged me: ‘Please tell them to cut my hand off, Mum. I can’t take this any more.’

Deryn was nauseous and, worse, had become addicted to his anti-sickness drugs. He was allowed a dose every seven to eight hours but within an hour of being given some, he would press the buzzer to call the nurses back in.

One in 7 Billion: Deryn Blackwell begins his hospital ordeal aged 10

‘When can I have my cyclizine?’ he would ask. ‘It’s the only thing that helps with the pain. It makes me feel safe. It doesn’t hurt for a little while, just long enough to forget about it. Then it all comes back again.’

If he was told to wait, Deryn would get angry and aggressive, like someone hooked on heroin. I had known drug addicts and, just weeks short of his 14th birthday, my son was ticking all the same boxes.

We couldn’t sit by and watch him spend his last days in a morphine fog. Enough was enough. So I went into the city and purchased a vaporiser pen – specialist equipment for inhaling an illegal drug…

Deryn had suffered enough. In 2010, when he was just ten years old, he had been diagnosed with leukaemia.

Eighteen months later, he was told he had a secondary cancer, the extremely rare Langerhans cell sarcoma. Only 50 cases have ever been recorded and only five people in the world currently have it. But no one had ever been found to have the two cancers combined, making Deryn unique. One boy in seven billion people.

By 2013, after nearly four years of hospital treatment, it seemed that the only thing left for him were opiate drugs to ease the pain as he reached the end of his life.

Like any mother would be, I was desperate to find something to alleviate his suffering.

I spent hour after hour researching on the internet, and that’s where I came across reports of a substance called Bedrocan, a cannabis-based painkiller that wasn’t available in the UK. Surely Bedrocan had to be a better option than mind-numbing morphine?

But the doctor told me that while it was effective, it had not been tested on children and she couldn’t prescribe it.

And so we took a decision that will horrify many parents reading this – and horrified me, too.

After all, I’d never seen anything positive come of smoking cannabis, and in my days working in nightclubs, illegal drugs had been my enemy. But if it could help my darling boy escape his daily torment, I was willing to try it.

Now we had to find some cannabis and then work out how to make the liquid that could ease Deryn’s pain.

Simon, my husband, arranged to meet someone at a nearby service station to collect some. The whole experience was frightening.

Cannabis was a class B drug, which carried a sentence of up to five years’ imprisonment for possession, and up to 14 years for supplying to another person.

We had seen news reports on TV about parents who had had their children taken away from them after trying alternatives such as cannabis. I hadn’t forgotten one doctor’s words to me about my child being made a ward of court if we went against traditional treatment methods.

If either of us were to get into trouble over this, Simon wanted it to be him. And he took responsibility for the operation. He wasn’t going to allow anyone to take me away from the children just for alleviating Deryn’s suffering.

Deryn smiles with his mother Callie and father Simon in 2013

Back at the hospital, meanwhile, our son’s latest bone marrow transplant had failed. Staff were giving up on him. It seemed Deryn’s death was a done deal and now all we could do was wait until he drew his final breath. If there was no improvement in two weeks, he would be placed in palliative care.

If ever I needed a sign to get a grip on myself, this was it. I had to remain positive, no matter what the doctors were telling me.

After further research, I discovered we needed to buy a rice cooker and vegetable glycerine to make the ‘tincture’ suitable for the vaporiser pen. The house stank to the heavens as Simon experimented with the infusion.

Deryn, of course, was excited to be trying it with the blessing of his mum and dad, but I felt anxious at the prospect of my son’s underage and illegal drug use, especially as we were in hospital.

After drawing the curtains so that no one could see through the window, Simon handed the filled pen over to Deryn. We felt like naughty schoolkids who were having a sneaky cigarette around the back of the bike sheds.

Deryn sucked on the pen, breathed in and blew out a massive cloud of vapour – and we frantically waved our hands around trying to disperse it, although there wasn’t the smell of cannabis. It smelt more like popcorn. After ten minutes, Deryn said that the pain had decreased a little and he felt more relaxed – the words we had been longing to hear.

He took the honey-like liquid - and the pain stopped

Alas, his condition continued to worsen. By December 2013, Deryn had moved out of hospital and into a hospice, where he planned his own funeral. His bravery attracted national attention and some of his favourite celebrities, including Paul Hollywood, Pauline Quirk and Linda Robson came to meet him.

Deryn was actually looking forward to dying and considered it his next adventure. But one night, he woke up in the early hours of the morning, sobbing. After staying so strong for so long, he was begging for me to end it all.

‘I don’t want any more morphine, Mum. It makes me feel like I’m not here,’ he cried.

I was sitting next to him, a nightly vigil, and held his hand. Once again, the situation seemed quite desperate. What would happen, I wondered, if I gave Deryn a small amount of golden cannabis tincture directly in his mouth? The vaporiser had brought him some relief but could a higher dose have better results?

I took a small, empty syringe from the medicine cupboard in the hospice and quickly checked that there was no one outside. It was New Year’s Eve so staff levels were minimal. I drew up 5ml of the honey-like substance, which had a sweet, floral flavour.

Still sobbing uncontrollably, Deryn opened his mouth and I popped the syringe underneath his tongue. Deryn held it for a minute before swallowing. Half an hour passed. He was no longer having a panic attack. He looked peaceful. I asked him how he was feeling.

‘I feel relaxed,’ he told me. ‘I’m aware of everything. I just feel at peace, Mum. It’s beautiful.’

Moments later, the nurse came back in with his dose of cyclizine, the powerful anti-sickness drug to which Deryn had grown addicted.

I panicked. There was no way he would turn that drug away and I was worried about the effect the cannabis tincture could have on it. Then I heard Deryn tell the nurse he didn’t want it. She was flabbergasted. Everyone knew how much he relied on it to help him.

Amazing... but this could be a one-off By Dr Ellie Cannon, MoS Resident GP It is baffling to hear about Deryn’s story. Any parent in Callie’s situation would have felt the desperation she felt and compulsion to help her son who was suffering so badly. Families do turn to alternative therapies, internet-based solutions and even outlandish claims that could help their child become pain-free and survive. At the end of life particularly, it is understandable to feel that conventional medicine may have failed and look elsewhere. This truly sounds like a miracle story: remission of cancer spontaneously is not a common occurrence. But I would be cautious for anyone to conclude that cannabis cured Deryn’s cancer or his infection. This is a true anecdote, and, admittedly, an astounding one, that happened involving one patient and therefore does not prove anything scientifically. Until the results are repeated in numerous patients, it could simply be the case that the use of cannabis coincided with the natural progression of his disease. I would warn others against trying anything similar. Advertisement

‘I don’t feel like I need it any more, thanks,’ he said, before rolling over and going to sleep.

Over the coming days, my priority was allowing him to die with his faculties intact, so whenever Deryn felt a twinge somewhere, I would put another 5ml of the tincture underneath his tongue and, within a few minutes, he felt good again.

Deryn’s mouth, fingers, stomach, gums, tongue, hips, knees, legs and back had been constantly painful for as long as I could remember, so this was nothing short of fantastic.

One evening, I heard Deryn yell: ‘Mum – look!’ The bandage on his middle finger had worked its way loose and completely come off, showing his third finger – which had been blackened and dead – had now healed. How on earth had a child with no immune system and no way of fighting infection managed to heal himself after being off medication for more than three weeks?

I called Deryn’s team to tell them what had happened. Not one of them could give me any answers.

We knew his bone marrow wasn’t functioning and it was not scientifically possible for his wounds to heal. Deryn had spent months in isolation because a common cold could be fatal – yet, somehow, he had overcome three catastrophic infections.

Hundreds of people had been praying for Deryn, blessing him in their own ways. Was this a miracle?

Later that evening, the hospice doctor arrived. ‘We’re no longer sure Deryn is dying,’ she admitted.

The doctors were not sure whether or not the hospice was now the best place for us.

When we’d arrived four weeks earlier, he’d been given three days to live. Now here he was a month later, in far better health than when he’d left his hospital room. They had no idea how this was possible.

Then it dawned on me. Only one thing had changed since Deryn started to recover: the cannabis tincture. I couldn’t tell the doctors what we’d done.

I was sure the authorities wouldn’t see it the same way as we did but if there was even a minuscule chance that the cannabis tincture was responsible for my son still being alive, I wasn’t willing to risk stopping it.

Deryn, centre right, with his parents and brother Dylan in 2013

I wanted to tell the world, share it with everyone, including the doctors so that they could help others, but I knew it was too dangerous to breathe a word to anyone in a position of authority.

Yet there was a direct correlation between Deryn having the cannabis tincture and his improved blood counts. Whenever he didn’t have it, they dropped. It was enough hard evidence to suggest that cannabis tincture was playing a vital role in his recovery. I hadn’t imagined in my wildest dreams that it could have saved Deryn’s life.

Since then, Deryn has gone from strength to strength. His unique story has led to me being contacted every week by parents who are desperate for a miracle similar to the one we were granted.

I have trusted many of them with the truth and pointed people towards the same path we took. Deryn went back to school in Norfolk where he thrived among his friends and peer group and, following just nine months of schooling in the space of four years, he left in June 2016 with seven GCSEs.

Now 17, his weight is no longer a problem and he has decided to pursue a career as a vegan chef.

That irony is not lost on us, but maybe years of eating bland hospital food gave him a passion for more flavoursome and exotic dishes. He’s good at creating them too.

As each day passes, the prospect of cancer returning decreases.

I’ll probably never be totally free of that fear, and if he so much as coughs my hair stands up on end.

I am reminded of my miracle boy every time I look at Deryn and I know deep in my heart that whatever the future may throw at us, we can cope.

We always do.

© Callie Blackwell, 2017

Extracted from The Boy In 7 Billion, by Callie Blackwell with Karen Hockney. It is published on April 6 by Mirror Books, priced £12.99. Offer price £9.74 (25 per cent discount) until April 2. Pre-order at www.mailbookshop.co.uk or call 0844 571 0640 – p&p is free on orders over £15.