Glenn Campbell has done countless pieces to camera in the two decades-plus he has been reporting on politics for BBC Scotland. Political births, deaths, the occasional marriage, he has looked directly into the lens and told viewers what’s what. Nothing, however, will ever have as much impact as the reports he delivers in a new documentary showing tonight on BBC1. My Brain Tumour and Me is a first-rate dispatch from the front line of the cancer battle, and contains some of the most extraordinary scenes you are likely to see on television this year.