We were going to give out about Gok Wan's abominable show again (8.00pm, Channel 4, he even has Vanessa Feltz on it tonight, FFS), instead we'd rather focus on our mental health. This is the second part of the special documentary, which considers where the line between sanity and mania lies, see ten volunteers come together for an extraordinary test. With five 'normal' volunteers and five who have been officially diagnosed as mentally ill, Horizon asks if you can tell who is who. Over five days, the group takes part in a life-changing experience as they are put through a series of challenges - from performing stand-up comedy to mucking out cows - to see who copes best with the tests put before them. The events are designed to explore the character traits of mental illness and ask whether the symptoms might be within all of us. The programme explores the labels associated with psychiatric disorders and questions our perceptions and preconceptions of what mental illness is.