Chelsea striker Liam Delap has recently stunned fans on Instagram by apparently doing incredibly complicated calculations in his head, finding what’s known as the cube root of some very large numbers.

But is he really a human calculator? Or is there something else going on? Tim Harford speaks to Rob Eastaway, mathematician and author of ‘Maths on the Back of an Envelope’ to learn about the trick you can use to pull this off - and while he’s here we also ask him about the trend of more goals being scored in the Premier League.

Presenter: Tim Harford