More or Less: Behind the Stats - The maths of spies and terrorists

After the killing of a British soldier on the streets of Woolwich in London, it emerged that the suspects were known to the security services. But how feasible is it for the authorities to keep track of everyone on their watch list? Tim Harford crunches the numbers, with the help of the former head of MI5, Dame Stella Rimington. Plus: a listener requests a cost-benefit analysis of kidney donations; and Johnny Ball gives the Apprentices a maths lesson.

Start the Week - Eric Schmidt on the New Digital Age

On Start the Week Emily Maitlis talks to the Executive Chairman of Google, Eric Schmidt about the digital future. A future where everyone is connected, but ideas of privacy, security and community are transformed. Former Wikileaks employee James Ball asks how free we are online. The curator Honor Harger looks to art to understand this new world of technology. And worried about this brave new world? David Spiegelhalter, offers a guide to personal risk and the numbers behind it.

Producer: Katy Hickman.