Our food system is one of the most successful, most innovative and most destructive industries on earth. It sustains us, but it is also killing us. Henry Dimbleby, co-founder of fast food chain Leon, creator of the National Food Strategy and author of Ravenous: How to get Ourselves and our Planet Into Shape, speaks to journalist and editor Rosie Boycott about how we can take action to make things better, drawing on health, farming, and environmental and food security.