Slavery was regarded in later 18th‐cent. Britain as essential to the exploitation of the West Indian colonies and there was strong opposition to any interference with the institution, particularly from centres like Bristol and Liverpool. The moral objections to slavery arose mainly from the evangelical movement of the second half of the century, reflecting concern for the spiritual and physical welfare of all mankind. A national committee of nine quakers and three Anglicans was set up in London in 1787, headed by Granville Sharp with Thomas Clarkson as secretary. It was decided to aim first at the suppression of the slave trade. In 1788 William Wilberforce, the son of a Hull merchant, joined the cause after his evangelical conversion, and supplied parliamentary leadership. He persuaded his friend William Pitt to give it unofficial backing and committees were set up in provincial towns, the most active being in Manchester. However, the abolitionist cause suffered from the reaction against the French Revolution. The agitation was revived by Clarkson's speaking tours in 1804, by which time the economic importance of the West Indies had lessened, and in 1807 Lord Grenville, an early convert, gave his government's backing to an abolition bill, forcing it through the Lords.
The campaign to abolish slavery itself throughout the British empire began in earnest in 1823, when the Anti‐Slavery Society was formed in London by evangelicals, quakers, and methodists. A campaign during the 1830 general election encouraged Grey's government to put through a bill abolishing slavery in the British empire in 1833, substituting apprenticeship for seven years.