One in four people in the UK experience a mental health problem, yet despite being so widespread, people rarely talk openly or candidly about it. For those who have these difficulties, this stigma can exacerbate their situation and make it harder to recover.
In this two-part series, a group of ten unlikely runners living with or affected by different mental health issues train for the ultimate test of mind over matter. They'll compete in one of the world's most famous endurance races - the 2017 London Marathon. Mental and physical health is closely linked, and taking up sport or exercise can benefit our psychological wellbeing, but this is no easy ride.
Nick Knowles is on a personal mission to get the runners across the finishing line and leads a team of running experts, nutritionists and psychologists. The runners are running in the London Marathon for Heads Together, a campaign set up by the Duke and Duchess of Cambridge and Prince Harry to tackle the stigma around mental health.
