Adam Kay is the author of one of the most successful books of the last couple of years, 'This is Going to Hurt', which is based upon his diaries from his former career as a doctor before he quit medicine.    He wrote down his often hilarious experiences as a way to cope with the stresses and emotions of his job.   He talks to Krishnan about how the world of medicine needs to change, challenging politicians and his worries for the future of the NHS.   Producer: Rachel Evans