Adam Pearson has made his name as a broadcaster and actor, including a role opposite Scarlett Johanssen in the 2013 movie Under the Skin. But it’s his severe facial disfigurement, caused by genetic disease Neurofibromatosis 1 (Nf1) – which could also cause him to lose his sight – that makes the 31-year-old instantly recognisable. Adam’s twin brother, Neil, has no outward signs of Nf1, yet it has caused severe memory loss and epilepsy. So why has the same disease affected the identical twins so differently? And what does the future hold for them? Adam’s affecting personal Horizon film, which he infuses with a quick wit, attempts to find answers to these big questions.