This commercial expansion and prosperity was sustained in part by the booming slave trade. While slavery was illegal within Britain itself, by the 18th century it was a fully established overseas industry, dominated by Britain and the American colonies.
Slaves came primarily from West Africa. Traveling on Britain ships in horrible conditions, they were taken to America and the Caribbean, where they were made to work on tobacco and sugar plantation. The living and working conditions for slaves were very bad. Many slaves tried to escape and other revolted against their owners in protest at their terrible treatment.
There were, however, people in Britain who opposed the slave trade. The first formal anti-slavery groups were set up to by the Quakers in the late 1700s, and they petitioned Parliament to ban the practice. William Wilberforce, an evangelical Christian and a member of Parliament, also played an important part in changing the law. Along with other abolitionists (people who supported the abolition of slavery), he succeeded in turning public opinion against the slave trade. In 1807, it became illegal to trade slaves in British ships or from British ports, and in 1833 the Emancipation Act abolished slavery throughout the British Empire. The Royal Navy stopped slave ships from other countries, freed the slaves and punished the slave traders. After 1833, 2 million Indian and Chinese workers were employed to replace the freed slaves. They worked on sugar plantations in the Caribbean, in mines in South Africa, on railways in East Africa and in the army in Kenya.