November 2021 saw the 240th anniversary of perhaps the darkest episode in the grim history of the British slave trade: the mass murder of 133 Africans from the Liverpool ship Zong. The subsequent claim for insurance by the ship’s owners, the Gregsons, for those deaths remains a landmark in the litany of barbarities perpetrated on Africans being forcibly transported over the Atlantic Ocean.


Zong’s owners claimed that, as the result of navigational errors, the ship was running short of water as it headed to Black River in Jamaica. To save the rest, it was decided to throw 133 enslaved Africans overboard. It remains unclear who gave the order as the captain, Luke Collingwood, was mortally sick, but the crew obligingly embarked on the mass killing. When Zong finally docked, it discharged 208 African survivors, who were, it must be assumed, absorbed into the plantation system of western Jamaica.

When the Gregsons claimed compensation for their maritime commercial loss, the insurers refused to pay so they were taken to court. Had they not gone to law, it is likely the Zong massacre would have remained hidden. The law case ­– or rather the insurers’ appeal against the initial judgement in favour of the Gregsons – was heard before Lord Justice Mansfield and two colleagues in 1783. It prompted outrage among a small band of people, and their incensed reaction was to fuel the early moves towards the abolition of the British slave trade.

Freed slave and abolitionist Olaudah Equiano
Freed slave and abolitionist Olaudah Equiano was just one campaigner who spread word about the 'Zong' case. (Photo by: Universal History Archive/Universal Images Group via Getty Images)

Granville Sharp – a dogged campaigner against the slave trade and long-term defender of Africans in Britain – heard about the case from the freed slave and abolitionist Olaudah Equiano. Sharp tried (unsuccessfully) to persuade the Admiralty to bring murder charges against the crew. He also turned to the Quakers who, soon afterwards, launched their own agitations against the slave trade. Quaker petitions, writings, agitation (and their publication of the now-famous image of the slave ship Brooks in 1788), formed the effective start of the campaign against the slave trade. It was a campaign that traced its roots back to the Zong outrage. Though the Zong itself was subsumed into the broader campaign against the horrors of the slave ships, it was that ship which acted as a catalyst, propelling key players – Equiano, Sharp, the Quakers – to rouse public and political awareness. Parliament and the public at large soon became aware of the brutal realities of slave trading.

The words used by Lord Mansfield in the case form a chilling reminder of the essential nature of Atlantic slave trading: “The case of the slaves was the same as if horses had been thrown overboard. It is a very shocking case…”

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Why were the enslaved people killed?

Before the Zong case in 1783, the legal question of how insurance claims were affected should Africans be deliberately killed had not arisen. For that was all the Zong affair was concerned with: insurance. The massacre had been explained under a plea of necessity, forced on the crew by a shortage of water.

The massive expansion of European trade to India and the Americas in the 17th and 18th centuries prompted the growth of complex maritime insurance. In the case of slave ships, enslaved Africans were insured as cargo, each with a value on his or her head.

Diagram of the slave ship Brooks, showing enslaved people crammed below decks
This drawing of the Liverpool slave ship 'Brooks' was commissioned by abolitionists to depict how Africans were crammed below decks. (Photo by GraphicaArtis/ Getty Images)

English law accepted that ‘natural death’ (simply dying or committing suicide) was not covered by insurance. If Africans died in a shipwreck or were killed in a revolt, however, then “the insurers must answer”. For years, if a ship’s crew had to abandon ship, they would leave the Africans entombed below to a terrible fate.

Yet why murder enslaved people, who had been bought at such cost and effort? After all, the aim was to deliver Africans in good health to the markets of the Americas. From start to finish, slave trading was a violent business kept in place only by draconian measures and savage punishments for any form of resistance. Chains and manacles were vital on all slave ships, so too were weapons to subdue, punish and deter.

The persistent threat of African resistance made killings a common atrocity

Though it may seem contrary to the owners’ economic interests, the persistent threat of African resistance made killings a common atrocity. The Atlantic slave trade was a history marked by savage fighting. Revolts were sometimes nipped in the bud – and followed by exemplary reprisals, often before the assembled survivors. Occasionally, the Africans won, but much more often they were crushed and punishments doled out to the defeated.

Africans wounded in fighting at sea posed a problem for ship masters. Injured Africans would, in the words of one captain, give “an unfavourable impression”. The obvious solution was to jettison the wounded overboard, then claim for them on the ship’s cargo insurance.

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Was this the case just for British insurance?

Though the murderous reality of the Zong affair was English, the killing of Africans at sea was common throughout the international trade in African humanity. All of Europe’s major colonial powers and the traders in the Americas had horrific examples of murdering Africans on their ships. We also know that mass killings continued on slave ships as long as the Atlantic trade continued until the 1860s.

All slave trading nations defined and treated enslaved Africans as cargo. The Dutch spoke of them as “stock”; and the French as “moveable stock”; while Portuguese insurance law classified slaves alongside beasts of the field.

Africans on slave ships everywhere were items of trade, just as they were to be on plantations in the Americas. All had a value, except for the old and infirm, who, in the unforgiving language of plantation ledgers, were “worthless” or “useless”.

All slave trading nations defined and treated enslaved Africans as cargo. The Dutch spoke of them as 'stock'; and the French as 'moveable stock'

The Zong case focuses attention – then and now – on this central fact: that the enslaved were treated as chattel. It provides a brutal illustration of the essential nature of Europe’s slave empires, and on the sea routes which sustained them. Though the mass murder seen on Zong in 1781 was exceptional in the numbers involved, it exposes a mentality underpinning the wider story of Atlantic slavery.

A major obstacle to a better understanding of the Zong story has been the public perception of Britain as an abolitionist nation. Britain’s abolition of the slave trade in 1807 and the United States following suit in 1808 have become a smoke screen, obscuring what happened before those years (ie when Britain was the dominant player in the North Atlantic slave trade).

How did the slave trade change in the early 19th century?

After 1808, the British and US navies operated abolitionist patrols to intercept illegal slave ships, but their efforts did not stop the flow of Africans across the Atlantic. It was during the years of that 19th-century slave trade that there were many more example of mass killings – some comparable to the Zong.

We know more about those incidents largely because they were reported by officers serving on those abolitionist patrols, with accounts of Africans pitched overboard from Brazilian and Portuguese ships being leaked to the press. They contained grotesque accounts of huge casualty rates among sick Africans as they were jettisoned alongside the dead. And slave ship captains often chose to throw Africans overboard rather than be caught and have their cargo impounded.

For the Royal Navy, this abolitionist activity involved an astonishing volte-face. Throughout the 18th century, navy ships had been a mainstay of the British slave trade: guarding routes and colonial outposts against European rivals, and suppressing slave revolts by shipping men and equipment. British warships were feared as much by the enslaved Africans as they were by European rivals.

And yet, after 1807, this mighty naval force turned 180 degrees: its men and ships henceforth being used for abolitionist purposes. This transformation was to have a major impact on the growing public awareness about the killing of Africans at sea.

Despite the British and American naval pressure and aggressive British diplomacy, the Atlantic trade continued, mainly with France, Spain, Portugal, Brazil and North Americans flying under false flags. More than 3 million Africans were shipped between 1808-1862, mainly to Brazil and Cuba.

The US no longer needed more Africans: there, the slave population was growing rapidly and fuelling a major internaltrade. Huge numbers were moved south and put to work in the cotton industry, and there were around 4 million slaves living in the US by the time of the American Civil War in the 1860s.

While Brazil too had its own largescale domestic slave trade – mainly in the new coffee plantations – there was a continuing demand for more Africans (as did Cuba for its sugar and tobacco industries). As this demand powered the 19th-century trade, more horror stories of overcrowded ships, African mortality and mass killings as slave ships made a dash across the South Atlantic proliferated.

During the 19th century, the west turned. Abolition became a major theme in European societies, notably British and also in North America. An increasingly literate public was appalled, via press reports, by the seaborne outrages against enslaved Africans, and eager to absorb the evidence and graphic images spilling from the Atlantic ships and the plantations. This was the setting for JMW Turner’s great painting The Slave Ship.

JMW Turner's oil painting, 'The Slave Ship'
JMW Turner's oil painting, 'The Slave Ship'. (Image by Alamy)

The world of print (think Uncle Tom’s Cabin) brought the realities of Atlantic and plantation slavery to unprecedented numbers of people. They were horrified by the centuries-old system that had reduced millions of Africans to the status of cargo, to be bought, sold, bequeathed, and inherited much like beasts of the field. At times, they died in much the same way.

The west was confronted by irrefutable evidence that Africans were still enduring ferocious levels of cruelty – and killings at sea. But it is, after 240 years, still the Zong case that remains the most infamous of mass killings on a slave ship, and the catalyst for change.


James Walvin is professor emeritus of history at the University of York and author of The Slave Trade (Thames & Hudson, 2011), The Zong: A Massacre, the Law and the End of Slavery (Yale University Press, 2011), and Freedom: The Overthrow of the Slave Empires (Robinson, 2019)

Explore more content from week four of our Regency course:

Slavery and Abolition, with Dr Lizzie Rogers – watching time 12 mins

The children who fought for the abolition of slavery – reading time 10 mins

The Haitian Revolution: the enslaved Africans who rose up against France – reading time 8 mins

Did George III support the slave trade? – reading time 7 mins

African American abolitionists in Britain – listening time 43 mins

9 key places connected to the abolition of the British slave trade – reading time 13 mins

David Olusoga on the extraordinary story of Olaudah Equiano - reading time 10 mins