Tim Harford speaks to Persi Diaconis, top professor of maths and statistics and legendary magician. The Stanford University professor and co-author of the book "Magical Mathematics" has an enthralling story to tell of how he discovered magic as a boy, and then, as a consequence, a love of maths. And to illustrate how closely maths and magic are linked, Crossing Continents editor and the BBC's in-house magician, Hugh Levinson, performs a mathemagical card trick - see the performance below. This programme was broadcast on the BBC World Service. The interview was recorded in 2011.