From Wikipedia

Empire: How Britain Made The Modern World

Episode Three

The Mission

Continuing his exploration of the British Empire, Professor Niall Ferguson retraces the journeys of Victorian explorer Dr David Livingstone. As well as pushing for the abolition of slavery, Livingstone and other missionaries dreamed of converting Africans and Asians to their own brand of Christianity, despite the Indian Mutiny, which showed vividly the dangers associated with imposing British values : for both the preachers and the men whose 'salvation' they desired.

Under increasing pressure from the abolitionist movement, Britain enacted the Slave Trade Act in 1807 which abolished the slave trade in the Empire. In 1808, Sierra Leone was designated an official British colony for freed slaves. The Slavery Abolition Act passed in 1833 made not just the slave trade but slavery itself illegal, emancipating all slaves in the British Empire on 1 August 1834.