WS More or Less: The world’s most diverse city

Is London the most diverse city in the world? The new London mayor Sadiq Khan has claimed that it is, but is he right? How is diversity measured? This month, British mathematician Sir Andrew Wiles will go to Oslo to collect the Abel prize, a prestigious maths prize for his work proving Fermat’s last theorem. Science author Simon Singh explains his work. Producers: Laura Gray and Ed Davey.