The slave trade was officially abolished throughout the British Empire in 1807. This documentary reveals one of Britain's darkest secrets: a form of slavery that continued well into the 20th century - the story of Indian indentured labour. "Coolies: How Britain Reinvented Slavery" tells the astonishing and controversial story of the systematic recruitment and migration of over a million Indians to all corners of the Empire. It is a chapter in colonial history that implicates figures at the very highest level of the British establishment and has defined the demographic shape of the modern world. Combining archive footage and historical evidence the programme includes interviews with Gandhi's great-grandaughter, Uma Dhupelia-Mesthrie, about Gandhi's campaign to end indentured labour and David Dabydeen - author and academic - whose great-grandfather was an indentured labourer in British Guyana.