Medical cannabis experts and advocates, Hannah Deacon and Professor Mike Barnes, sit down with their guests to find out why cannabis matters to them. ---In July 2010, Callie Blackwell’s eldest son, Deryn, was diagnosed with Acute Lymphoblastic Leukaemia and just 18 months later a rarer, more aggressive form of cancer, Langerhans Cell Sarcoma. After years of chemotherapy, radiotherapy and failed bone marrow transplants, 10 days after his 14th birthday, Deryn was given just three days to l...