Tim Harford on income inequality in the UK, and elsewhere. He speaks to Professor Sir Tony Atkinson of Oxford University; Stewart Lansley, author of 'The Cost of Inequality'; and Professor Donald Boudreaux of George Mason University. Also, David Spiegelhalter, the Winton Professor of the Public Understanding of Risk at Cambridge University explains why he took on what could be his riskiest venture to date - appearing on BBC One's Winter Wipeout. Plus, the magic of maths with magician and Stanford maths professor Persi Diaconis.