What would a sustainable economy look like? How could we live within our environmental means? Sir Dieter Helm explains what it would take to properly maintain different types of capital, why polluters would have to pay, why the current generation would have to fund the necessary maintenance of our natural assets and why we would have to save to invest. Author of Net Zero and The Carbon Crunch, Helm is Professor of Economic Policy at the University of Oxford. From 2012 to 2020 he was Independent Chair of the UK Natural Capital Committee, providing advice to the government on the sustainable use of natural capital. His latest book is Legacy: How to Build the Sustainable Economy and he is in conversation with Mark Lloyd, CEO of The Rivers Trust.