The Slavery Abolition Act 1833 abolished slavery throughout the British Empire except "the Territories in the Possession of the East India Company ," the "Island of Ceylon," and "the Island of Saint Helena."
Slavery has been illegal in England itself for over 900 years.
This was highlighted during
Somersett's Case of 1772. James Somerset was an enslaved African who was bought by Charles Stewart in Boston and brought with him to England in 1769.
Somerset escaped in 1771 but was recaptured in November of that year. Somerset's three godparents from his baptism as a Christian in England asked a court to determine whether or not Somerset's imprisonment was legal.
The court held that chattel slavery was unsupported by the common law in England and Wales, though the position elsewhere in the British Empire was left ambiguous (until 1833). Slavery had never been authorised by statute in England and Wales, and Lord Mansfield's decision found it also unsupported in common law. Lord Mansfield limited his judgment to the issue of whether a person, regardless of being a slave, could be removed from England against his will, but even this reading meant that certain property rights in chattel slaves were unsupported by common law.
It was this case which was one big factor in slaves in America fleeing to Britain, where they could live as free men.
Somerset v Stewart - Wikipedia, the free encyclopedia