Slavery in Britain was finally abolished in 1833, but it led to another mass movement of people as indentured labour was introduced to replace slaves. In this, the British took two million labourers from India to work in harsh conditions in colonies around the world.
These places include the Caribbean (Guyana, Trinidad), Africa (Kenya, Uganda, South Africa), the Pacific (Fiji) and the Indian Ocean islands (Mauritius). The picture is of Indian labourers or ‘coolies’ who’ve just arrived in Trinidad in 1897.
UNESCO.org section on the Slave Trade.
Encyclopaedia Britannica entries on Slavery and Slave Trade
United Nations Interregional Crime and Justice Research Institute section on Human Trafficking