Richard Thaler: Is a nudge enough to change our behaviour?

From Covid to climate change, governments around the world face challenges which demand modifications of human behaviour. When it comes to getting people to do things differently, what works best: the carrot of persuasion, or the stick of coercion? Stephen Sackur speaks to Richard Thaler, the world renowned economist and behavioural scientist who believes a nudge often works better than a shove when change is needed. Does that hold good when the problems we face become urgent and existential?