World on the Move: on Start the Week Andrew Marr explores how the mass movement of people has changed societies, in a special edition broadcast in front of an audience as part of a day of programmes on BBC Radio 4. The historian Sir Hew Strachan looks back at the largest single influx of people into Britain when 250,000 Belgians arrived during the Great War, while Frank Dikötter explores the biggest forced internal migration as tens of millions of young Chinese were sent to work in the countryside during the Cultural Revolution. The poet Patience Agbabi humanises the mass movement of people with her tale of one refugee's story. And what of those who return? The Bangladeshi author Tahmima Anam looks at what happens when you try to go back home.