In 1493 Christopher Columbus arrived in Spain with the news of his discovery of a new continent. Just 10 years later the trans-Atlantic slave trade began, with the first Africans being taken by Spanish merchants to the Americas as slaves in 1503.
Over the next three centuries around eight million Africans were exported across the Atlantic, many of them on English ships.
Even more lucrative than the slave trade itself though were the plantations of the Caribbean, where slave labour produced sugar demanded by European consumers. In the 18th century sugar was worth its weight in gold and many of Britain's most powerful families had profited hugely from slavery.
Yet in 1807 the British parliament voted to end Britain's involvement in the slave trade. So why did Britain choose to abolish a trade which had made it so wealthy?
Most attention this bicentennial year will focus on Bristol and Liverpool, the great slaving ports, and London, the focus of the elite abolitionists' activities. But the reality is that the ending of the slave trade was driven by a national moral and political campaign, which was energised by the power and radicalism of the new industrial cities of northern England.
Much of the radicalism of cities like Leeds was inspired by religious dissent. After 1750 Leeds' Quakers, Baptists and Methodists led the moral attack on the slave trade, which grew as popular support for overseas missionary efforts increased.
The Leeds Intelligencer reported on 5 March 1792 that the city's inhabitants wondered how African converts could be won when they suffered 'the cruelty and injustice of those Christian States who are the authors of their present misery'.
Such ethical concerns produced a series of petitions for abolition which reflected Leeds' growing civic pride. 'Let us not, my friends, be backward in so laudable a business... This borough hath not been the last in other generous and humane designs. Let it not on this occasion be said, that we want either religion or humanity' (Leeds Intelligencer, 1788). (Oldfield)
The abolition of the slave trade had been debated in parliament through the 1780s and 90s but it was not until the general election of 1806 that the government accepted that the issue could no longer be ignored.
In Leeds the campaign to elect the MPs for Yorkshire focused almost entirely on the slave trade and repeatedly threatened to result in violence. Religious leaders promised to mobilise their followers' votes only for candidates who declared their support for abolition.
Meetings of industrial workers argued that slavery was an abuse of the dignity of labour. Campaign songs referred to 'sable brethren', and even appealed to women (who did not have the vote): 'The Fair, whose soft Bosoms are Sympathy's Shrine, This Foe of the Woman-born traffic will join. O muster your Charms on Humanity's Side' (Drescher).
William Wilberforce almost lost the election because his refusal to support the immediate freeing of all slaves enabled his more radical opponents to argue that he had formed a secret alliance with slaving interests.
On returning to parliament he convinced other MPs of the strength of popular pressure for the ending of the slave trade. Britain's involvement in the slave trade was finally ended in 1807, though slavery itself was not abolished in the British Empire until 1833.
Dr Shane Doyle, University of Leeds.
Dr Doyle is the author (along with Henri Medard) of a new book, Slavery in the Great Lakes Region of East Africa, to be published in November 2007.