Many humanitarians, however, were eager to use British power to do good, and they constituted a significant lobby. Anti-slavery was the most urgent cause. When in 1814 Castlereagh successfully pressed the French to agree to abolish their slave trade in five years’ time, this delay was denounced as the “death warrant of a multitude of innocent victims” and a huge national campaign was organized, claiming 750,000 supporters. Wellington tried to renegotiate the treaty, and the government put pressure on its allies Spain and Portugal, the main slave-buying nations, to stop the trade. Castlereagh wrote: “You must really press the Spanish…there is hardly a village that has not met and petitioned.” London even asked the Pope for support. Castlereagh persuaded the reluctant Great Powers to attach to the Treaty of Vienna (1815) a condemnation of the slave trade—the first such “human rights” declaration in a major international treaty. This began a long effort to end slaving, against the resistance of the slave-trading and slave-holding nations and their African suppliers.
Campaigning peaked in 1833 with more than 5,000 petitions, containing nearly 1.5 million signatures. One, more than a mile long, was signed and sewn together by women, who played an unprecedented part in the campaign, among them Elizabeth Heyrick, author of Immediate, Not Gradual Abolition (1824). Parliament responded in 1834 by emancipating 800,000 slaves in the empire, paying a huge £20m in compensation to the owners—equal to a third of the state budget—and requiring a four-year “apprenticeship” by slaves. This was thus a compromise measure, but still its anniversary was publicly celebrated annually by American abolitionists as a great achievement. In 1843 British subjects were forbidden to own slaves anywhere in the world. The abolition of slavery in the empire in practice applied to slave ownership by whites. Greatly affected was the Cape Colony, one of the most rigid and oppressive slave societies in history. The “Boers” (Dutch-speaking settlers) responded by trekking out of British territory, outraged that black people were “placed on an equal footing with Christians, contrary to the laws of God.” Traditional forms of servitude remained endemic in Africa and Asia, however, and in places still remain; and colonial authorities were very cautious about tackling them.
Even when other states agreed to outlaw slave trafficking—sometimes (as with Spain and Portugal) with compensation paid by Britain—they commonly winked at evasion. So the Royal Navy placed a permanent squadron from 1808 to 1870, at times equal to a sixth of its ships, to try to intercept slavers off West Africa. It was based at Freetown, the capital of the colony for freed slaves at Sierra Leone, which had the first African Anglican bishop, Samuel Crowther, rescued as a boy from a slave ship by the Royal Navy. Patrolling was a thankless and gruelling effort, exposing crews to yellow fever, hardship and even personal legal liability for damages; it also cost a large amount of taxpayers’ money. France and the United States refused to allow the Royal Navy to search ships flying their flags. There was continual diplomatic friction with slave-trading states. British officials there were often threatened with violence. During the 1830s and 1840s several American ships forced by bad weather into British colonial territory had the slaves they were carrying released. In 1839 in the famous case of the slave ship Amistad, when captives rebelled and killed the captain, British testimony proving illegal action by American officials helped to secure their freedom. A serious dispute with the United States occurred in 1841 when American slaves on the ship Creole, being taken from Virginia to be sold in New Orleans, seized the ship and killed a slave-trader. They were given asylum in the British-ruled Bahamas, where they were acquitted of any crime and declared free.
Britain signed forty-five treaties with African rulers to stop the traffic at source. They were very reluctant to give it up, even threatening to kill all their slaves if they were prevented from selling them. In several cases, Britain paid them to abandon the traffic. Abolitionists urged that Britain should maintain a territorial presence in West Africa, to combat illegal trafficking and promote legitimate commerce, such as palm oil, to wean African rulers and Liverpool merchants away from slaving and towards soap manufacture—a good example of cleanliness being next to godliness. By 1830 palm oil exports were worth more than the slave trade. But the trade continued, and the Royal Navy adopted more aggressive tactics, including blockading rivers and destroying slave pens on shore, even when these were foreign property. In 1861 it occupied Lagos, deposing the ruler who refused to stop the trade, and thus blocked one of the main slave routes. Over sixty years the navy captured hundreds of slave ships off the African coast and freed some 160,000 captives. As one recalled it:
They took off all the fetters from our feet and threw them into the water, and they gave us clothes that we might cover our nakedness, they opened the water casks, that we might drink water to the full, and we also ate food, till we had enough.
Several hundred thousand more were prevented from being shipped from Africa by naval and diplomatic pressure.
Palmerston, as Foreign Secretary, was prepared to put pressure on slave-buyers too. In 1839 he simply ordered the seizure of Portuguese slave ships, and in 1845 his successor, Lord Aberdeen, declared Brazilian slave ships to be pirates, and 400 were seized in five years. In 1850 the Royal Navy even forcibly entered Brazilian ports to seize or destroy hundreds of slave ships—decisive in forcing Brazil, the biggest slave-buyer of all, to end one of the largest forced emigrations in history. Palmerston said this had given him his “greatest and purest pleasure.” Cuba, supplied by fast United States ships, came under similar pressure. But American ships were treated more cautiously, as searches of suspected slave ships carrying the Stars and Stripes caused threats of war from Washington. As Palmerston expostulated, “every slave trading Pirate” could escape by simply hoisting “a piece of Bunting with the United States emblems.” The American Civil War caused a reversal in American policy in 1862, when Abraham Lincoln’s government signed a secret treaty allowing the Royal Navy to intercept American slavers. The Spanish and Cuban authorities bowed to circumstances, and the Atlantic slave trade was effectively ended. Slavery itself remained legal in the United States until the 1860s, and in much of Latin America until the 1880s. As late as 1881 the Royal Navy arrested an American slave ship off the Gold Coast.
The British campaign against the slave trade has often been debunked. French and American slave-traders accused Britain of using it as a pretext to try to gain control of West Africa, Cuba, even Texas. Some later historians claimed that slavery ended only because it was no longer profitable. But recent research is practically unanimous that slavery was booming, and it would have been in Britain’s economic interests to expand it, as the United States did. But Britain was rich enough to let its powerful humanitarian and religious lobby get its way.
Did Britain—another accusation at the time and since—use the slave trade as a pretext for colonial expansion in Africa? In fact, successive gov-ernments were reluctant to rule inhospitable and relatively profitless territory, and movement inland was negligible until the late-nineteenth-century “scramble for Africa.” The exception, which involved campaigns against the aggressive slaving kingdom of theAsante (Ashanti)—a magnificent and exceptionally cruel warrior society—was done at the request of Africans on the coast, who were subject to repeated attack from the 1820s onwards and requested British protection. Central Africa meanwhile was being devastated by Muslim slavers supplying the Middle East. The Foreign Office estimated that they were taking 25,000–30,000 people per year during the 1860s, and the nineteenth-century total has been estimated at between 4 million and 6 million people, huge numbers dying as they were dragged across the Sahara or to the coast, and many others being killed in the violence of capture. British anti-slavery groups—inspired by the adventures and writings in the 1850s and 1860s of one of the most revered Victorian heroes, the working-class missionary and explorer David Livingstone—demanded government intervention in what Livingstone had rightly called the open sore of the world. He hoped optimistically that a “Christian colony” of “twenty or thirty good Christian Scotch families” would lead to moral and commercial improvement and would put an end to slavery. Instead, a long diplomatic effort was required to throttle the trade, by persuading African rulers to stop supplying and Muslim states to close the great slave markets of Egypt, Persia, Turkey and the Gulf. Britain had far less power to act directly in the Muslim world, where slavery had ancient social and religious sanction, so action had to be discreet. The consul-general at Cairo in the 1860s, Thomas F. Reade, spied out the Egyptian slave markets disguised as an Arab. He estimated that 15,000 Africans were sold in Cairo annually, and reported on “the cruelties and abominations” involved. Other diplomats were active in helping escaped slaves, including by purchasing their freedom with official funds, and the consul in Benghazi maintained a safe house for escapers at his own expense. British interference in the slave trade—however cautious Whitehall tried to be—could cause serious tensions and even led to mass uprisings in Egypt and the Sudan. However, careful but persistent high-level pressure on the Egyptian, Turkish and Persian governments to forbid the trade, backed up by naval patrols, treaties and even bribes to officials to apply the law, eventually had considerable effect. Pressure and financial inducements to the sultan of Zanzibar (a vast slaving entrepôt) shut its slave market in 1873. Pressure on Egypt resulted in an Anglo-Egyptian Convention of 1877 to end the trade, and in 1883 a similar convention was signed with the Ottoman government. Further afield, the navy even patrolled off Australia to stop “blackbirding” (bringing quasi-slaves from Fiji and other Pacific islands) for the sugar plantations of Queensland.
Britain pressed for the insertion of an anti-slavery agreement in the 1885 Berlin Act on the partition of Africa, though it was notoriously unequally applied. As a Foreign Office official noted in 1896, Britain, “with small military means,” could only govern “countries full of Arabs…with the assistance of the Arabs.” Moreover, the partial abolition of slavery was no panacea—indeed, it gave rise to other social and economic problems. There was a huge multiplication of indentured labour, particularly of Indians shipped to theCaribbean and Africa, who were also highly exploited. Suppressing the slave trade meant at first unsaleable slaves being held by African rulers, and treated even more cruelly. Generally, the British stopped slave trading and abolished slavery as a legal status in territories they controlled in Africa and India (often with financial compensation to the slave-owners), so that slaves could free themselves—which many did. The colonial official Frederick Lugard claimed that 55,000 became free without violence in northern Nigeria between 1902 and 1917. Gradual abolition weakened the brutal hierarchies of slave-owning societies, indirectly benefiting women and the young. The fact that emancipation was supervised by “alien and disinterested authorities” smoothed the process.