The British were (in fact) against Slavery!
The first anti-slavery statement by Dutch and German Quakers was signed at Germantown, Pennsylvania in 1688. Following this, English Quakers had begun to express their official disapproval of the slave trade since 1727 and promote reforms. From the 1750s, a number of Quakers in Britain's American colonies also began to oppose slavery, calling on English Quakers to take action, and encourage their fellow citizens, including Quaker slave owners, to improve conditions for slaves, educate their slaves in Christianity, reading and writing, and gradually emancipate them.
An informal group of six Quakers pioneered the British abolitionist movement in 1783 when the London Society of Friends' yearly meeting presented its petition against the slave trade to parliament, signed by over 300 Quakers. They subsequently decided to form a small, committed, non-denominational group so as to gain greater Anglican and Parliamentary support.
In 1807 the British Parliament voted to abolish the slave trade and enforce this through its maritime power.
Slavery continued on a large scale in the United States of America.
Britain played a prominent role in the Trans-Atlantic slave trade. Slavery was a legal institution in all of the 13 American colonies and Canada (acquired by Britain in 1763).
In 1785, English poet William Cowper wrote: We have no slaves at home Then why abroad? Slaves cannot breathe in England; if their lungs receive our air, that moment they are free. They touch our country, and their shackles fall. Thats noble, and bespeaks a nation proud. And jealous of the blessing. Spread it then, And let it circulate through every vein.
Following many years of lobbying by the Abolitionist movement, the British Parliament voted to make the slave trade illegal anywhere in the Empire with the Slave Trade Act 1807. Thereafter Britain took a prominent role in combating the trade, and slavery itself was abolished in the British Empire with the Slavery Abolition Act 1833. In 1811, Arthur William Hodge was the first slave owner executed for the murder of a slave in the British West Indies. He was not, however, as some have claimed, the first white person to have been lawfully executed for the killing of a slave.
Slavery in the United States was a form of slave labor which existed as a legal institution from the early colonial period. After the American Revolution (1775-1783), the northern states all abolished slavery, and Congress prohibited slavery in the Northwest Territory. By the 1850s the South was vigorously defending slavery and its expansion into the territories. In the North a small number of abolitionists denounced it as sinful, and a large number of anti-slavery forces rejected it as detrimental to the rights of free men. Compromises were attempted and failed, and in 1861 eleven slave states broke away to form the Confederate States of America. To defeat the Confederacy, the Union in 1862 made abolition of all slavery a war goal, which was achieved in 1865. All the slaves were freed and the owners received no compensation. http://en.wikipedia.org/wiki/Slavery_in_the_United_States
On 4 February 1794, the First Republic (Convention) voted for the abolition of slavery in all French colonies. The abolition decree stated that "the Convention declares the slavery of the Blacks abolished in all the colonies; consequently, all men, irrespective of colour, living in the colonies are French citizens and will enjoy all the rights provided by the Constitution."
Restored by the Consulate in 1802, slavery was definitively abolished in 1848 by the Second Republic, on Victor Schoelchers initiative.
1775 April 14 The Society for the Relief of Free Negroes Unlawfully held in Bondage holds four meetings. Re-formed in 1784 as the Pennsylvania Abolition Society, Benjamin Franklin would later be its president.
17761783 American Revolution
Pennsylvania becomes the first then-U.S.-state to abolish slavery.
1846: Under British pressure the Bey Tunisia outlawed the slave trade; the policy was reversed by his successor. 1847: Under British pressure the Ottoman Empire abolishes slave trade from Africa
1849: Treaty between Britain and Persian Gulf states to suppress slave trade
1873: Slavery abolished in Puerto Rico 1873: Treaty between Britain and Zanzibar and Madagascar to suppress slave trade  1874: Britain abolishes slavery in the Gold Coast (now Ghana), following its annexation in 1874.