The mom of a cancer-stricken teenage boy has revealed she gave her son cannabis “to ease his pain” – and has made a miraculous recovery.

Callie Blackwell and her husband Simon, of Norfolk, decided to give her teen son Deryn the Class B drug after he became addicted to the anti-sickness drugs he was being given at hospital.

In her new book – “The Boy in Seven Billion” – Callie tells the story of her then 10-year-old son being diagnosed with leukemia in 2010 and Langerhans Cell Sarcoma – a rare and aggressive cancer, two years later.

Deryn, now 17, has since defied doctors by surviving two deadly cancers.

The youngster is dubbed the “boy in seven billion” because he is thought to be the only person to have had both conditions at the same time.

His mum Callie detailed in her book how they made the decision and the “frightening” experience of finding cannabis and administrating it to their son.

In an excerpt in the Mail on Sunday, Callie said: “Deryn was nauseous and, worse, had become addicted to his anti-sickness drugs.

“We couldn’t sit by and watch him spend his last days in a morphine fog. Enough was enough.”

She added: “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.”

She said she spent hours researching online before buying a vaporizer pen – a specialist equipment for inhaling drugs.

Her husband Simon then arranged to meet someone at a nearby petrol station to pick the illegal drug – which carries a sentence of up to five years’ imprisonment for possession.

Based on her online research, Callie was then able to make the “tincture” using a rice cooker and glycerine – suitable for the vaporizer pen.

She gave it to her son Deryn, who by then, had moved out of hospital and into a hospice.

Callie said: “After 10 minutes, Deryn said that the pain had decreased a little and he felt more relaxed – the words we had been longing to hear.”

After the cannabis use continued, Callie claims her son’s finger – which had been black and dead – was beginning to heal after he had “no immune system and no way of fighting of infection.”

She also claims doctors later told her they were “no longer sure Deryn” was dying.

Since then Deryn left the hospice and went back to school to take his GCSEs.

He left school in June 2016 with seven GCSEs and wants to pursue a career as a chef.