How Were the Chibok Girls Released?

82 Nigerian schoolgirls were freed from Islamist group Boko Haram in exchange for a number of its fighters in May. Drew Hinshaw from the Wall Street Journal tells Weekend how their release was secured.

Also in the programme: How a British highway exposes the country's divisions.

(Picture: Some of the girls from Chibok released from Boko Haram captivity. Credit: STEFAN HEUNIS/AFP/Getty Images)