Over the past five years, the number of obese people needing hospital treatment has more than trebled, and as people get bigger, moving the super-obese to and from hospital has become a challenge as traumatic for patients as it is dangerous for health staff. But a new type of patient has led to a new kind of ambulance on Britain's streets, one that can shift people who weigh up to 70 stone - the bariatric, or 'supersize', ambulance. This documentary follows Thames Ambulance's bariatric service, one of the busiest in the UK, as it takes us into the lives of its patients, giving a unique and contemporary insight into Britain's 'Big Society', and its impact on individual lives and public services. Narrated by Liza Tarbuck. 'Cause that matters.