Who are Insulate Britain and what do they want?

For the past few months Insulate Britain have been blocking roads in an effort to pressure the government into sealing up the UK's leaky, draughty housing-stock. So why are a group of eco-activists facing confrontations from angry drivers, and even risking injury, for insulation? Shivani Dave speaks to environment correspondent Matthew Taylor about Insulate Britain's demands and explores the possible health benefits of properly insulated homes with Dr James Milner