Emily Whitehead was diagnosed with acute lymphoblastic leukaemia 14 years ago. The initial prognosis was hopeful, but her treatment did not go well. Emily, who was just five, reacted badly to the standard course of chemotherapy, which caused severe pains in her legs. About two years after her diagnosis, by which time most childhood sufferers are in the clear, the American schoolgirl suffered a relapse. The doctors recommended further intensive bouts of chemotherapy and a bone-marrow transplant, if she was strong enough.

Emily’s parents, Tom and Kari, agonised about the best course of action. They learnt that only 30 per cent of children who have a bone-marrow transplant live another five years. Kari scoured the internet to find out as much as she could about Emily’s condition. Though she trusted the doctors treating her daughter, Kari wanted a second opinion. She arranged to visit the Children’s Hospital of Philadelphia.

During Emily’s treatment, her parents had done their best to make the most of every moment with her. Emily loved exploring the countryside with her father and, on walks near their home in Phillipsburg, New Jersey, she spotted porcupines and tried to identify different bird songs. Tom continued to take Emily on these expeditions during breaks in her treatment, even though she sometimes struggled to walk.