The story of how a line on a map becomes a hard state border that no one can cross.

This is a special edition that 10-14 year olds can also enjoy, but if you are not in that age bracket we hope that there’s something in it for you too. It’s a trial and we’d love to know what you think. Email [email protected] or tweet @bbctheinquiry – thanks to Niko, Christina and Sophie for your feedback. The Inquiry will be back to normal next week.

(image 2018: A North Korean student attends a class at Kang Pan Sok revolutionary school outside of Pyongyang. Credit: Ed Jones/Getty Images)