William is a GP in Reading and set up the national Health Walk Programme and Green Gyms in the mid 1990s. He then worked at the Met office forecasting NHS demand and then Natural England where he started Green Social Prescribing. He has been an advisor to WHO on physical activity training for health professionals and is an honorary prof. at University Exeter. His main interest is using physical activity to treat and prevent disease. He is CEO of Intelligent Health an organisation that has engaged 2 million people to get them more active through Beat the Street. Other current roles are Chair Active Essex and Chair of West Midlands Combined Authority Physical Activity Coalition.