Hannah Fry (University College London) talks about her work on the mathematics of data and reveals her favourite problem modelling the behaviour of people in crowds. The second part of the interview in which Hannah talks about an application to track down serial killers is here: https://www.youtube.com/watch?v=UsRfECCPsCY Interview with Dr Tom Crawford from the University of Oxford, recorded at the Isaac Newton Institute. Produced by Tom Crawford, with thanks to Hannah Fry, the Isaac Newton Institute, and James Messinger. For more maths related fun check out Tom's website https://tomrocksmaths.com/ Follow Tom Crawford on Facebook, Twitter and Instagram @tomrocksmaths. https://www.facebook.com/tomrocksmaths/ https://twitter.com/tomrocksmaths https://www.instagram.com/tomrocksmaths/ Get your Tom Rocks Maths merchandise here: https://beautifulequations.net/collections/tom-rocks-maths