The anti-slavery campaign
Britain went from being the most active slave-trading country at the turn of the nineteenth century to showing the most vehement opposition in only a few generations. Factors that pushed Britain to turn against slavery were many ? economic, revolutionary, political, societal, and religious. The history of abolition by the British ? first of the slave trade and then of slavery - involved the campaigning efforts of key individuals and the mobilization of the masses.
Why did the British begin to change their attitude to the transatlantic slave trade at the point where it seemed to have been so economically successful? There are many reasons, and their relative importance continues to be debated. Social, religious, political, economic and revolutionary forces were all clearly at work. There was social and ideological change in the Enlightenment period and slavery sat uncomfortably alongside the free-trade economy of the industrial revolution in Britain. Some have argued that the economic value of the plantations fell, following the loss of the North American colonies in 1783. Although the attractiveness of cane sugar and other crops produced by plantation slaves declined in the face of the new industrial economy in Britain with technologically advanced production methods, there is evidence that the West Indies were operating profitably as late as the 1820s. Others point to the intervention of religion and especially the role of the Quakers and the nonconformist churches as agents of change. The Society of Friends (the Quakers) put forward their objections to slavery as early as the late 1600s, produced the first anti-slavery literature in the 1760s, and presented their first petition to Parliament in 1763. They were ignored as eccentrics. John Wesley, the founder of the Methodist movement, was a vociferous critic of the slave trade and published his ?Thoughts Upon Slavery? in 1774.
Advertising bill for abolition A series of rebellions and revolts throughout the Caribbean and the southern states of America, as well as political and social reform and an effective anti-slavery movement, finally ended first the slave trade and then the institution of slavery itself. The revolution in Haiti, by defeating thousands of French and British troops, made the continuation of the transatlantic slave trade seem untenable. It was clear that if slavery was not abolished, then slaves might well emancipate themselves.
The work of some former slaves contributed to the anti-slavery movement (most notably Ottabah Cugoano, Olaudah Equiano and Mary Prince) as did the ongoing resistance and rebellions in the colonies. There were also British people who were prepared to come forward and testify to the inhumanity of slavery, including John Newton, a sea captain in the slave trade who later became an Anglican priest and author of the hymn ?Amazing Grace?.
Course of events
Several court cases, such as that concerning the infamous slave ship ?Zong? in 1781 brought the harsh reality of the trade to the attention of a widening public in Britain. There was also a growing legal problem relating to the position of enslaved Africans in Britain. Granville Sharp brought the controversial test case of James Somerset to court and in 1772 it was ruled that enslaved people in England, Wales and Ireland could not be forced to return to the Caribbean, which was wrongly interpreted to mean that all slaves in Britain were free.
Although there had been criticisms of, and protests against, slavery since its inception, the first mass anti-slavery society was formed in 1787 by twelve men including Thomas Clarkson and Granville Sharp. This was the Society for Effecting the Abolition of the Slave Trade. The group quickly recruited William Wilberforce to act as its political mouthpiece in Parliament. The first Bill to abolish the slave trade was introduced in the House of Commons in 1791 by Wilberforce but it was rejected. The following year the Commons voted in favour of abolishing the slave trade but the bill was rejected by the House of Lords. Despite several more failed attempts the abolitionists persevered and finally, on 25 March 1807, helped in large part by the successful revolution in Haiti the British Parliament passed an Act abolishing the transatlantic slave trade in British colonies. Although this ended the transportation of Africans across the Atlantic, it did not stop other European countries trading, or end the institution of slavery itself. It was not until 1833 that an Act of Parliament was passed which, when it became law in 1834, ended slavery itself. Even then, full emancipation was not realized until 1838 when a period of apprenticeship failed.
 Although they treated slaves less harshly, some Quakers were still slave owners. In America, Quakers who in time freed their slaves paid them compensation. That was not the case in Britain.