Migrant crisis: 'A century of exile and homelessness'

In 2015, the war in Syria and economic hardship in parts of Africa led to record levels of migration in Europe.

Some experts have advised caution over the numbers, stressing that mass movement of people has been an even greater challenge for the international community at key points in the past century, including World War Two and the wars in Vietnam and the Balkans.

World Affairs Editor John Simpson looks back at "a century of exile and homelessness".