Callie Blackwell, mother and author of 'The Boy In 7 Billion', discusses their journey with TRE's Selina MacKenzie...

Deryn Blackwell is a walking, talking miracle. At the age of 10, he was diagnosed with Leukaemia. Then 18 months later he developed another rare form of cancer called Langerhan's cell sarcoma. Only five other people in the world have it. He is the youngest of them all and the only person in the world known to be fighting it alongside another cancer, making him one in seven billion. He and his parents were told that there was no hope of survival and so at the age of 14, after four years of intensive treatment, exhausted by the fight and with just days to live, Deryn planned his own funeral. But on the point of death Deryn's condition suddenly and dramatically changed. His medical team had deemed this an impossibility, his recovery was nothing short of a miracle. Unexplainable. However, Deryn's desperate mother, Callie was hiding a secret....