By Gavin Stamp
Business reporter, BBC News
More than 10 million Africans were transported to the Caribbean
Two hundred years after Parliament voted to abolish it, the British slave trade remains a highly emotive and contentious subject.
The extent of this institutionalised trade in human cargo, the degree to which those involved profited from it and the steps that their descendants should take to recognise this and make amends are all still matters of fierce dispute.
But one aspect of the trade is not generally contested.
That is that it had a major impact on the history and economic development of Africa, on the growth of Britain and its empire and on the future of Europe and the Americas.
For nearly 350 years from the start of the 16th century, it is estimated that tens of millions of Africans were forcibly removed from their continent and sold around the world.
This movement constituted the largest forced migration of a human population in history, says one leading African historian.
Follow dynamic trails across Africa, the Caribbean and the UK with text, images and audio to explore the abolition of British slavery
"The transatlantic slave trade obviously had a major effect on the growth of the population in Africa," says Dr Hakim Adi, from the University of Middlesex, adding that its population stagnated between 1500 and 1900.
The trade was predicated on the supply of cheap labour to plantation owners in the Americas and the Caribbean.
Despite often horrific working conditions, plantation owners got eight years of work - on average - out of their slaves while African rulers received European goods in return.
The trade's so-called "economic triangle" was completed by the large supplies of sugar, cotton, tobacco, molasses and rum, all fruits of slave labour, exported back to Europe.
The precise value of the slave trade has never been truly calculated but there is little doubt that for some prominent individuals, it was highly lucrative.
Stately homes such as Harewood House in Leeds and much of the architectural splendour of cities such as Bristol and Liverpool, from which the majority of British slaving voyages departed, bear witness to the financial rewards of the trade.
It is generally acknowledged that international trade in slave-produced goods was more profitable for financial investors than that of most homegrown products - although historians say returns varied greatly depending on the industry.
But the trade, they agree, quickly became a vicious circle with sugar, tobacco and coffee becoming must-have items for people at all levels of society, necessities which Britain's foreign policy increasingly sought to defend.
The debate about the degree to which the slave trade underpinned Britain's growth as an industrial power is a controversial one with some historians arguing that it has been overstated and that its economic value eroded significantly before its eventual abolition.
Others are less equivocal, arguing that it generated the capital to invest in industrial infrastructure and provided the raw material for major employers like cotton mills.
Dr Ali says the "human resources that were taken from Africa contributed to the capitalist development and wealth of Europe".
One in 10 slaves died every year on plantations, estimates suggest
Apologies for Britain's role in the slave trade have been plentiful in recent years, with a recent statement of sorrow from Tony Blair adding to expressions of regret from Liverpool and the Church of England, which owned a Barbados plantation worked by slaves.
"There is no doubt that there were members of the Society who were successful slave traders and that industries like sugar and cotton all benefited," says D'Arcy Parkes, from the Society of Merchant Venturers, a merchant's guild which ran Bristol's port for 400 years.
But he stresses that no descendants of slave traders are now members and that the city is no longer home to any shipbuilders or sugar companies.
"It was an abhorrent practice and we are not in any way trying to excuse it."
Despite these recognitions of past mistakes, claims of corporate links to the slave trade still surface regularly and several of Britain's largest companies have been forced to address allegations that they prospered from the practice.
Countering claims that it made profits from slavery, sugar giant Tate & Lyle says founder Sir Henry Tate only entered sugar refining in 1859.
SLAVE TRADE FACTS
More than 2,000 ships set sail from Bristol on slaving voyages
More slaves were taken to Brazil than any other country
At its height, 75% of plantation sugar was shipped to London
Historians claim the King of Dahomey was paid £250,000 a year for selling slaves
"When Henry Tate and Abram Lyle established their businesses in 1859 and 1865 respectively, the slave trade had been illegal in Britain for more than 50 years," the firm says.
"Neither family was previously connected to the sugar trade."
Barclays has rejected claims that two of its family members were slave traders, arguing that David Barclay, as a Quaker, was a prominent opponent of the practice.
Lloyds of London was sued in 2004 by descendants of black American slaves who claimed that by insuring slave ships, the body was an accessory to the trade.
The lawsuit was dismissed and all appeals have so far been rejected.
Claims that companies still in business benefited commercially from the slave trade are difficult to corroborate.
Sugar business Tate & Lyle says it had no links with the slave trade
A case in point is cigarette maker Imperial Tobacco, which was formed at the start of the 20th Century by a merger of several firms including Wills & Co.
Formed in 1786, Wills ran a tobacco store in Bristol and imported produce from the US.
The Bristol Record Office, whose archives hold documents relating to both Imperial Tobacco and Wills, says there is a chance that the firm was involved indirectly in slave-related trade but Imperial Tobacco says it has no evidence of such a link.
Some US firms, however, have felt the need to acknowledge a degree of complicity, however indirect.
In the most high-profile example, investment bank JP Morgan Chase apologised to staff after admitting that two companies which later became part of its global operation had accepted slaves as collateral for loans between 1831 and 1865.
Calls for business to be more self-examining about the slave trade's legacy are part of a wider debate over whether and how victims of the practice should be compensated.
Various claims are being pursued, the most striking being a $777 trillion damages case lodged by the World Reparations and Repatriation Truth Commission.
Bristol has admitted the slave trade enriched many local businessmen
The Ghana-based body says Africa was systematically and unlawfully stripped of its human resources for more than 400 years.
Some African politicians have dismissed these efforts, saying they ignore the fact that generations of African leaders are descended from slave-owning families.
But others feel some form of financial redress is needed, alongside a campaign to promote understanding of slavery, to help right a wrong of such economic and moral proportions.
"We do believe in reparations," says activist David Pott, who is organising a month-long march from Hull to London to mark the trade's abolition.
"If we just said sorry, I don't think that would be enough."
With additional research by Will Smale