The Slavery Abolition Act 1833 (3 & 4 Will. 4. c. 73) was an act of the Parliament of the United Kingdom which abolished slavery in the British Empire by way of compensated emancipation. The act was legislated by Whig Prime Minister Charles Grey, 2nd Earl Grey's reforming administration, and it was enacted by ordering the British government to purchase the freedom of all slaves in the British Empire, and by outlawing the further practice of slavery in the British Empire. The Act explicitly delineated 19 separate pots of compensation covering the Caribbean, South Africa, and Mauritius. Although Britain, Canada, Australia, and New Zealand were technically included, these had relatively few slaves at this time for other reasons. India was excluded. Around 800,000 freed slaves were attested in the claims process.
While the 1833 Act was a landmark, it did not end slavery throughout the entire British sphere of influence. The Act explicitly excluded territories like British India, where slavery was addressed separately by the Indian Slavery Act, 1843. In regions colonised later, such as Nigeria, the abolition of pre-existing local systems of slavery was a gradual process that extended into the early 20th century. Furthermore, in British protectorates, which retained their own local laws, the institution persisted for much longer. For example, slavery in Bahrain was not legally abolished until 1937.
Slavery had been judged to be without legal basis in England in 1772. In May of that year, Lord Mansfield's judgment in the Somerset case emancipated a slave who had been brought to England from Boston in the Province of Massachusetts Bay, and thus helped launch the movement to abolish slavery throughout the British Empire. The case ruled that slavery had no legal status in England as it had no common law or statutory law basis, and as such someone could not legally be a slave in England. However, many campaigners, including Granville Sharp, took the view that the ratio decidendi of the Somerset case meant that slavery was unsupported by law within England and that no ownership could be exercised on slaves entering English or Scottish soil. Ignatius Sancho, who in 1774 became the second recorded black person to vote in a British general election — the first being John London — wrote a letter in 1778 that opens in praise of Britain for its "freedom, and for the many blessings I enjoy in it", before criticising the actions towards his black brethren in parts of the Empire such as the West Indies.
By 1783, an anti-slavery movement to abolish the slave trade throughout the Empire had begun among the British public, with the Society for Effecting the Abolition of the Slave Trade being established in 1787. The Wedgwood anti-slavery medallion by Josiah Wedgwood was, according to the BBC, "the most famous image of a black person in all of 18th-century art". Fellow abolitionist Thomas Clarkson wrote: "Of the ladies several wore them in bracelets, and others had them fitted up in an ornamental manner as pins for their hair. At length, the taste for wearing them became general; and thus fashion, which usually confines itself to worthless things, was seen for once in the honourable office of promoting the cause of justice, humanity and freedom."
Spurred by an incident involving Chloe Cooley, a slave woman brought to Canada by an American loyalist, the Lieutenant-Governor of Upper Canada, John Graves Simcoe, tabled the Act Against Slavery in 1793. Passed by the local Legislative Assembly, it was the first legislation to outlaw the slave trade in a part of the British Empire. By the late 18th century, Britain was simultaneously the largest slave trader and centre of the largest abolitionist movement. William Wilberforce had written in his diary in 1787 that his great purpose in life was to suppress the slave trade before waging a 20-year fight on the industry.
Parliament passed the Slave Trade Act 1807 (47 Geo. 3 Sess. 1. c. 36), which outlawed the international slave trade in the British Empire, but not slavery itself. The legislation was timed to coincide with the expected Act Prohibiting Importation of Slaves by the United States, Britain's chief rival in maritime commerce. This legislation imposed fines that did little to deter slave trade participants. Abolitionist Henry Brougham realised that trading had continued, and as a new MP successfully introduced the Slave Trade Felony Act 1811 (51 Geo. 3. c. 23) which at last made the overseas slave trade a felony throughout the empire. The Royal Navy established the West Africa Squadron to suppress the Atlantic slave trade by patrolling the coast of West Africa. It did suppress the slave trade, but did not stop it entirely. Between 1808 and 1860, the West Africa Squadron captured 1,600 slave ships and freed 150,000 Africans. They resettled many in Jamaica and the Bahamas. Britain also used its influence to coerce other countries to agree to treaties to end their slave trade and allow the Royal Navy to seize their slave ships.
In 1823, the Anti-Slavery Society was founded in London. Members included Joseph Sturge, Thomas Clarkson, William Wilberforce, Henry Brougham, Thomas Fowell Buxton, Elizabeth Heyrick, Mary Lloyd, Jane Smeal, Elizabeth Pease, and Anne Knight. Jamaican mixed-race campaigners such as Louis Celeste Lecesne and Richard Hill were also members of the Anti-Slavery Society.
During the Christmas holiday of 1831, a large-scale slave revolt in Jamaica, known as the Baptist War, broke out. It was organised originally as a peaceful strike by the Baptist minister Samuel Sharpe. The rebellion was suppressed by the militia of the Jamaican plantocracy and the British garrison ten days later in early 1832. Because of the loss of property and life in the 1831 rebellion, the British Parliament held two inquiries. The results of these inquiries contributed greatly to the abolition of slavery with the Slavery Abolition Act 1833.
Up until then, sugar planters from rich British islands such as the Colony of Jamaica and Barbados were able to buy rotten and pocket boroughs, and they were able to form a body of resistance to moves to abolish slavery itself. This West India Lobby, which later evolved into the West India Committee, purchased enough seats to be able to resist the overtures of abolitionists. However, the Reform Act 1832 swept away their rotten borough seats, clearing the way for a majority of members of the House of Commons to push through a law to abolish slavery itself throughout the British Empire.
Though the British parliament had the right to pass legislation on matters that applied to the individual colonies in the British Empire, the loss of the Thirteen Colonies in the American War of Independence made legislators in London nervous about imposing their will on the sugar colonies in the Caribbean. Each British West Indian colony had its own legislature, and, in the view of the Colonial Office, involvement of those bodies would help the process of emancipation.
Through the 1820s, both abolitionists and the Colonial Office had a policy of "gradualism", fearful that sudden emancipation might be disadvantageous to the slaves as much as to the plantation owners. The first step was a process termed "amelioration". This included teaching the slaves Christianity, legalising slave marriages, banning the separation of slave families by sale and reducing the use of whips to impose discipline. The Sunday markets, where slaves could sell produce they had raised in their own time, should be moved to another day (respecting the Sabbath). Slaves were to be allowed to own property and, in limited circumstances, to give evidence in court. Another target was to give slaves the right to buy their own freedom, with the intention of encouraging them to save money from their own work. The abolitionists did not trust the individual colonies to pass legislation that met their needs. The Order in Council of 1824 put in place the amelioration provisions. Though developed in consultation with the West India lobby in London, it was met with the fullest criticism by those who operated plantations. They argued that the resulting damage to profitability required compensation. The amelioration measures were only partially implemented by the colonies, leaving the Colonial Office with the job of obtaining fuller compliance. Also, the British Government was now faced with the issue of compensation: something that had not been included in their plans.