What contribution did the slave-based trade with the Americas make to the fast-industrialising economy of 18th-century Britain, and how do Britons today benefit from the prosperity this era?

Slave-owning planters, and merchants who dealt in slaves and slave produce, were among the richest people in 18th-century Britain. Profits from these activities helped to endow All Souls College, Oxford, with a splendid library, to build a score of banks, including Barclays, and to finance the experiments of James Watt, inventor of the first really efficient steam engine.

Liverpool merchant bankers, heavily involved in the slave-based trades, extended vital credit to the early cotton manufacturers of its Lancashire hinterland. West Indian planters built stately homes - some, ridiculously extravagant dwellings such as William Beckford's Fonthill - and furthered the modernisation of British agriculture by 'improving' their estates. Others invested in canals. And, of course, many spent their ill-gotten gains on gambling, prize fights and riotous living.

Consumers had little idea of the terrible human cost of production.

The plantations were themselves by-products of a new economic system. Plantation slavery thrived thanks to a consumer revolution that took place in Britain and the Netherlands in the 17th century. In these countries, consumer markets widened as farmers and manufacturers hired wage workers as the best way to expand output and sales.

The fact that farmers had to pay rent, and that labourers needed a job if they were to feed their families, was the germ of a new economic system - what we now call capitalism.

Many different types of people now needed money in their pocket or purse. They no longer produced the food they ate or the clothes they wore. The better-off bought fine wines or oriental silks. But even the day labourer could buy tobacco and sugar. Merchants met this new demand by setting up slave plantations in Virginia and the Caribbean. While there was a growing taste for exotic stimulants and luxuries, consumers had little idea of the terrible human cost involved in their production.

But those directly engaged in the Atlantic slave trade or plantations certainly knew of the terrible loss of life and the unrelenting toil of slavery. Planters and merchants bought Africans partly because they were better than white people at surviving in the tropics, and partly because they could deprive their African captives of any rights.

White servants were badly treated too, but there were limits when abuse exposed them to legal action and personal censure from their neighbours. Non-slaving colonists sometimes objected to the growing power of slave-owners, but it was fatally easy to let the Africans do all the harshest work. The planters soon discovered that they could play on white fears to construct a thoroughly commercial and racial version of an old institution - slavery.


The Atlantic boom


In his famous 1944 book 'Capitalism and Slavery', the Trinidadian scholar Eric Williams argued that profits from slavery 'fertilised' many branches of the metropolitan economy and set the scene for England's industrial revolution'.

His thesis has focused decades of debate and controversy. It correctly identified the very great intimacy in 18th-century Britain between making money from slavery on the one hand, and the financing of British capitalist development, on the other.

On the sugar estates the mills were kept going 24 hours a day, with enslaved people working 18-hour shifts

British capitalism was a cause rather than consequence of slave plantation development. But the fit between slave plantation growth and industrial advance in Britain was to be impressive and sustained. The plantation colonies supplied the mother country with a growing stream of popular luxuries - dyestuffs, sugar, tobacco, then later coffee and chocolate as well - and cotton, a crucial industrial input.

The availability of such treats drew consumers into greater participation in market exchanges and greater reliance on wages, salaries and fees. Baiting the hook of wage dependence, new consumer goods helped to motivate what some historians call the 'industrious revolution', the longer hours and tight labour control associated with industrialism.

The slave plantations themselves anticipated the intense organisation of labour, with coerced slave gangs working under the eye and whip of the slave driver. On all slave plantations hours of work were very long, but on the sugar estates the mills were kept going 24-hours-a -day, with enslaved people working at night as well, in 18-hour shifts.

The slave plantation colonies of the Americas not only supplied premium commodities, but were a captive market for metal tools, textiles and provisions. Indeed, the British empire of the early and mid-18th century became a zone of thriving trade in which the ability of New England and Newfoundland to sell provisions to the West Indies, and to participate in the Africa trade, also boosted their ability to buy English manufactures.

The boom in Atlantic produce also underpinned a huge programme of commercial ship-building and maintenance, with about a third of the English mercantile fleet being built in the North American colonies.


Slave-related trade

British merchants and manufacturers had a growing home market, growing colonial outlets and an ability to penetrate - legally or otherwise - the colonial and home markets of their rivals.

At crucial moments during the onset of industrialisation in Britain, colonial markets, colonial supplies and colonial profits made a significant contribution. Early capitalist manufacturers needed wider markets to reach the levels of output that would allow for the widespread adoption of new industrial methods.

The buoyancy of the Atlantic trade, including slaving, allowed merchants and bankers to supply credit

The ability of British merchants to penetrate European markets declined steadily in the 18th century, but the growth of transatlantic trade more than compensated for this. Some of this took the form of the famous triangular trade, whereby merchants from Bristol and Liverpool bartered trade goods for people on the African coast, then sailed to the West Indies or North America to sell the enslaved Africans, and finally took a cargo of plantation produce back to England.

The early industrial manufacturers had quite modest capital requirements for the purchase of machinery, but needed extended credit to reach overseas markets. An early cotton mill might cost no more than £1,000 but the manufacturer might need to invest 10 times this sum in wages and raw materials before they received any money back from from sales.

It often took a year or more for the manufacturer to receive payment from overseas. In the meantime, they needed to pay their workers and suppliers. This is where the merchants' credit came in. The buoyancy of the Atlantic trade, including profits on the trade in slaves and slave produce, put merchants and bankers in a position where they were willing and able to supply that credit.

Eric Williams anticipated many of these arguments, supplying telling quotations and anecdotes to illustrate them. But he did not attempt to quantify the overall contribution of Atlantic exchanges to British industrial growth in the period 1750-1820.

Some of his formulations seemed to focus only on the contribution of slave trade profits when account should be taken of the importance of all aspects of the slave-related trades. Later studies have explored the importance of colonial trade to British prosperity and growth.


Profit margins

Colonial purchases of British goods were a major stimulus to the economy. Around 1770, 96.3% of British exports of nails and 70.5% of the export of wrought iron went to colonial and African markets. Around the same time, British exports of iron manufactures took 15-19% of domestic iron production.

Textile exports accounted for between a third and a half of total production, with colonial and African markets again taking a huge share. In the periods 1784-1786 and 1805-1807, the growth of exports accounted for no less than 87% of the growth of British output.

Slave-generated profits could have covered a third of Britain's overall investment needs

During the French Wars (1793-1802, 1804-1815) British exporters often found that, excluded from Europe, they had to rely on colonial and American markets. The merchant and finance houses that facilitated the import of sugar and cotton also helped to extend badly-needed credit to the textile and metal manufacturers.

Around 1770, total investments in the domestic British economy stood at £4 million, (or about £500 million in today's money). This investment included the building of roads and canals, of wharves and harbours, of all new equipment needed by farmers and manufacturers, and of all the new ships sold to merchants in a period of one year.

Around the same time, slave-based planting and commercial profits came to £3.8 million (or about £450 million in contemporary terms). Of course profits were not all reinvested, but they did furnish a convenient pool of resources available for this purpose. British West Indian planting profits can be estimated at £2.5 million in 1770, while trading profits on the West India trade were around £1.3 million, at a time when annual slave trading profits were at least £1 million. Even if not all reinvested the slave-generated profits were large enough to have covered a quarter to a third of Britain's overall investment needs.

Notwithstanding the interruptions of war, the plantations made a very substantial contribution for many decades, indeed for the greater part of the century after 1720. Between 1761 and 1808, British traders hauled across the Atlantic 1,428,000 African captives and pocketed £60 million - perhaps £8 billion in today's money - from slave sales.

A study of the activities of 23 London merchants who were heavily involved in the slave trade found they 'played their part in building roads and bridges ... They invested in [other] maritime undertakings, especially whaling; the making of cloth, mainly wool; mining, especially salt, coal, and lime; and the production of building materials, such as lumber, rope, iron and glass.'

Inherited privilege

The broad case for a slave-related stimulus to the British economy is very strong. And it has been further reinforced by a recent study by academic Kenneth Pomeranz which has again underscored the contribution of American land, worked by enslaved people, to British growth in the 18th and early 19th centuries.

Using the telling concept of 'ghost acreage', we can consider the fact that Britain had available to it the fruits of the labours of millions of enslaved people, working millions of acres of highly fertile (and conveniently located) soil in the New World, helping it over the difficult humps of early industrialisation.

Enslaved people on the plantations of the Americas made a large contribution to British prosperity

It is estimated that the acreage required to grow the cotton, sugar and timber imported by Britain from the New World in 1830 would have been somewhere between 25 and 30 million acres - or more than Britain's total arable and pasture land combined.

By this time some European countries were refining sugar from beets, but this would have also required vast acreage. Wood could, perhaps, have been imported from elsewhere and was anyway not mainly logged by slave labourers. But as Pomeranz observes: raising enough sheep to replace the yarn made with Britain's New World cotton imports would have required staggering quantities of land, almost nine million acres in 1815 ... and over 23 million acres by 1830.'

One might add that cotton yarn was much more suitable for early industrial processes than wool, and that the price paid for each pound of raw cotton dropped by one half between 1790 and 1820 as an expanding slave population, the new cotton gin and steam transport opened the inland states to cotton cultivation.

While the acres of fertile land were an 'ecological windfall', the forced labour of several million enslaved people brought them swiftly into cultivation. As late as 1860, six million slaves toiled in the fields of the American South, Cuba and Brazil, producing vast quantities of cotton, sugar and coffee. The thousands of millions of hours of slave toil helped to underpin the global ascendancy of Victorian Britain.

Overall, enslaved people on the plantations of the Americas made a large and measurable contribution to British prosperity. While the idea of inherited guilt is wrong-headed - we are not responsible for our forebears' crimes and misdeeds - the idea of inherited privilege is perfectly valid.

Britain got off to a good start at the time of the Industrial Revolution, and Britons today still enjoy a consequent afterglow of prosperity.