Although it did not automatically emancipate those enslaved at the time, it encouraged British action to press other nation states to abolish their own slave trades.

On Sunday, 28 October 1787, Wilberforce wrote in his diary: "God Almighty has set before me two great objects, the suppression of the slave trade and the reformation of manners.

"[6] On 2 April 1792, William Wilberforce sponsored a motion in the House of Commons "that the trade carried on by British subjects, for the purpose of obtaining slaves on the coast of Africa, ought to be abolished."

He argued, however, that a vote for immediate abolition would be ineffective, as it would not prevent merchants from other countries from stepping in to continue the trade abandoned by the British.

Abolitionists argued that West Indian assemblies would never support such measures, and that making the abolition of the slave trade dependent on colonial reforms would cause indefinite delay.

At that time he told the House that proceeding too quickly would cause West Indian merchants and landowners to continue the trade "in a different mode and other channels.

"[12] He argued that "if the committee would give the time proposed, they might abolish the trade; but, on the contrary, if this opinion was not followed, their children yet unborn would not see the end of the traffic.

[14] The motion and resolutions did not receive consent in the House of Lords, however, consideration being formally deferred to a subsequent session on 5 June 1792, where they were never revived.

[16][17] Abolitionists’ numbers were magnified by the precarious position of the government under Lord Grenville, whose short term as prime minister was known as the Ministry of All the Talents.

After a debate lasting ten hours, the House agreed to the second reading of the bill to abolish the Atlantic slave trade by an overwhelming 283 votes for to 16.

[22] The United States adopted its Act Prohibiting Importation of Slaves on 2 March 1807, the same month and year as the British action.

Article 1, Section 9, Clause 1 of the United States Constitution forbade the closing of the slave trade for twenty years, until 1808.

Action was also taken against African kingdoms which refused to sign treaties to outlaw the trade, such as "the usurping King of Lagos",[citation needed] who was deposed in 1851.

[27] In the 1860s, David Livingstone's reports of atrocities within the Arab slave trade in East Africa stirred up the interest of the British public, reviving the flagging abolitionist movement.