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The Slave Ship (1840), J. M. W. Turner’s representation of the mass killing of enslaved people, inspired by the Zong killings.[1]
Wikimedia Commons

The Zong massacre was the murder of more than 130 enslaved African people by the crew of the British slave ship Zong on and in the days following 29 November 1781.[a]The number of deaths is unknown, but James Kelsall, Zong‘s first mate, later said that “the outside number of drowned amounted to 142 in the whole”.[2] The William Gregson slave-trading syndicate, based in Liverpool, owned the ship as part of the Atlantic slave trade. As was common business practice, they had taken out insurance on the lives of the enslaved Africans as cargo. According to the crew, when the ship ran low on drinking water following navigational errors, they threw enslaved Africans overboard.

After the slaver ship reached port at Black River, Jamaica, Zong’s owners made a claim to their insurers for the loss of the enslaved Africans. When the insurers refused to pay, the resulting court cases (Gregson v Gilbert (1783) 3 Doug. KB 232) held that in some circumstances, the murder of enslaved Africans was legal, and that insurers could be required to pay for those who had died. The jury found for the slavers but at a subsequent appeal hearing the judges, led by Lord Chief Justice, the Earl of Mansfield, ruled against the slave-trading syndicate owners, owing to new evidence that suggested the captain and crew were at fault.

Following the first trial, Olaudah Equiano, a freedman, brought news of the massacre to the attention of the anti-slavery campaigner Granville Sharp, who worked unsuccessfully to have the ship’s crew prosecuted for murder. Because of the legal dispute, reports of the massacre received increased publicity, stimulating the abolitionist movement in the late 18th and early 19th centuries; the Zong events were increasingly cited as a powerful symbol of the horrors of the Middle Passage, the transoceanic route by which enslaved Africans were taken to the New World.[3]

The non-denominational Society for Effecting the Abolition of the Slave Trade was founded in 1787. The following year the UK Parliament passed the Slave Trade Act 1788, its first law regulating the slave trade, which limited the number of slaves per ship. In 1791 parliament prohibited insurance companies from reimbursing ship owners when enslaved Africans were murdered by being thrown overboard.

The massacre inspired works of art and literature, and was commemorated in London in 2007, among events to mark the bicentenary of the British Slave Trade Act 1807, which ended British participation in the African slave trade, although it stopped short of outlawing slavery. A monument to the murdered enslaved Africans on Zong was installed at Black River, Jamaica.


Zong was originally named Zorg, meaning “Care” in Dutch, by its owners, the Middelburgsche Commercie Compagnie. It operated as a slave ship based in Middelburg, Netherlands, and made a voyage in 1777, delivering kidnapped Africans to the Dutch colony of Surinam in South America.[4] Zong was a “square stern ship” of 110 tons burthen.[2] The British 16-gun brig HMS Alert captured her during the Fourth Anglo-Dutch War on 10 February 1781. On 26 February, Alert and Zong arrived at Cape Coast Castle, in what is now Ghana. Cape Coast Castle was maintained and staffed, along with other forts and castles, by the Royal African Company (RAC),[2] which used the castle as its regional headquarters.[5]

In early March 1781, the master of William purchased Zong on behalf of a syndicate of Liverpool merchants,[6] which included Edward Wilson, George Case, James Aspinall and William, James and John Gregson.[7] William Gregson had an interest in fifty slaving voyages between 1747 and 1780, and served as mayor of Liverpool in 1762.[2] By the end of his life, vessels in which Gregson had a financial stake had carried 58,000 Africans to slavery in the Americas.[8]

Zong was paid for with bills of exchange, and the 244 slaves already on board were part of the transaction,[2] but the ship was not insured until after it started its voyage.[2] The insurers, another syndicate from Liverpool, underwrote the ship and its slaves for up to £8,000, approximately half the potential market value of the slaves; the remaining risk was borne by the owners.[2][9]


Zong was the first command of Luke Collingwood, formerly the surgeon on the William.[10] While Collingwood lacked experience in navigation and command, ship’s surgeons were typically involved in selecting captured Africans for purchase, so their medical expertise supported the determination of “commodity value” for a captive. If the surgeon rejected a captive, that individual suffered “commercial death”, being of no value and was liable to be killed by the African traders;[11] sometimes these killings happened in the presence of the surgeon. It is therefore likely that Collingwood had already witnessed the mass killing of slaves. The historian Jeremy Krikler has commented that this may have prepared him psychologically to condone the massacre that later took place on the Zong.[11][12][13] Zong‘s first mate was James Kelsall, who had also served on the William.[14]

The vessel’s only passenger, Robert Stubbs, was a former captain of slave ships. In early 1780 he was appointed by the African Committee of the Royal African Company as the governor of Anomabu, a British fortification near Cape Coast Castle in Ghana. This position made him also vice-president of the RAC Council of the Castle.[15] Owing to his ineptitude and enmity incurred with John Roberts, governor of the Castle, Stubbs was forced out of the governorship of Anomabu by the RAC Council after nine months.[15][16] Witness statements gathered by the African Committee of the RAC accused him of being a semi-literate drunkard who mismanaged the fort’s slave-trading activities.[17] Stubbs was aboard to return to Britain, and Collingwood may have thought his earlier experience on slave ships could be useful.[15]

Zong had a 17-man crew when it left Africa, which was far too small to maintain adequate sanitary conditions on the ship.[18] Mariners willing to risk disease and rebellions on slave ships were difficult to recruit within Britain, and were harder to find for a vessel captured from the Dutch off the coast of Africa.[19] Zong was manned with remnants of the previous Dutch crew, the crew of William, and unemployed sailors hired from settlements along the African coast.[20]

The Middle Passage

When Zong sailed from Accra with 442 enslaved people on 18 August 1781, it had taken on more than twice the number of people that it could safely transport.[20] In the 1780s, British-built ships typically carried 1.75 slaves per ton of the ship’s capacity; on the Zong, the ratio was 4.0 per ton.[4] A British slave ship of the period would carry around 193 enslaved people, and it was extremely unusual for a ship of Zong‘s relatively small size to carry so many.[21] After taking on drinking water at São Tomé, Zong began its voyage across the Atlantic Ocean to Jamaica on 6 September 1781. On 18 or 19 November the ship neared Tobago in the Caribbean, but failed to stop there to replenish its water supplies.[22]

It is unclear who, if anyone, was in charge of the ship at this point,[23] as Luke Collingwood had been gravely ill for some time. The man who would normally have replaced him, first mate James Kelsall, had been suspended from duty following an argument on 14 November.[24] Robert Stubbs had captained a slave ship several decades earlier, and he temporarily commanded Zong during Collingwood’s incapacitation, but he was not a registered member of the vessel’s crew.[25] According to the historian James Walvin, the breakdown of the command structure on the ship might explain the subsequent navigational errors and the absence of checks on supplies of drinking water.[26]


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Map of the Caribbean, showing Tobago, Hispaniola (red) and Jamaica (blue)
Wikimedia Commons

On 27 or 28 November, the crew sighted Jamaica at a distance of 27 nautical miles (50 km; 31 mi) but misidentified it as the French colony of Saint-Domingue on the island of Hispaniola.[27][28] Zong continued on its westward course, leaving Jamaica behind. This mistake was recognised only after the ship was 300 miles (483 km) leeward of the island.[27] Overcrowding, malnutrition, accidents and disease had already killed several mariners and approximately 62 Africans.[29] James Kelsall later claimed that there was only four days’ water remaining on the ship when the navigational error was discovered, and Jamaica was still 10 to 13 sailing days away.[30]

Plan of the slave ship Brookes, carrying 454 slaves. Before the Slave Trade Act 1788, Brookes had transported 609 slaves and was 267 tons burden, making 2.3 slaves per ton. Zong carried 442 enslaved people and was 110 tons burden – 4.0 slaves per ton.[21]
Wikimedia Commons

If the enslaved people died onshore, the Liverpool ship-owners would have had no redress from their insurers. Similarly, if they died a “natural death” (as the contemporary term put it) at sea, then insurance could not be claimed. If some enslaved people were thrown overboard to save the rest of the “cargo” or the ship, then a claim could be made under “general average”,[31] the principle under which a captain who jettisons part of his cargo to save the rest can claim for the loss from his insurers; the ship’s insurance covered the loss of slaves at £30 per person.[32]

On 29 November, the crew assembled to consider the proposal that some of the enslaved people should be thrown overboard.[33] James Kelsall later claimed that he had disagreed with the plan at first, but it was soon unanimously agreed upon.[32][33] On 29 November, 54 women and children were thrown through cabin windows into the sea. On 1 December, 42 male slaves were thrown overboard and 36 more followed in the next few days. Another 10, in a display of defiance at the inhumanity of the slavers, chose to commit suicide by jumping into the sea.[34] Having heard the shrieks of the victims as they were thrown into the water, one of the captives requested that the remaining Africans be denied all food and drink rather than being thrown into the sea, but the request was denied.[35] In total, 142 Africans had been killed by the time the ship reached Jamaica. The account of the King’s Bench trial reports that one slave managed to climb back onto the ship after being thrown into the water.[36]

The crew claimed that the Africans had been jettisoned because the ship did not have enough water to keep them all alive for the rest of the voyage. This claim was later disputed, as the ship had 420 gallons (1,909 L) of water left when it finally arrived in Jamaica on 22 December.[32] An affidavit later made by Kelsall stated that on 1 December, when 42 enslaved people were killed, it rained heavily for more than a day, allowing six casks of water, sufficient for 11 days, to be collected.[32][37]

Arrival at Jamaica

On 22 December 1781, Zong arrived at Black River, Jamaica with 208 slaves on board, less than half the number taken from Africa.[34] The survivors were sold into slavery in January 1782[38] at an average price of £36 per person. The Jamaican Vice-Admiralty court upheld the legality of the British capture of Zong from the Dutch and the syndicate renamed the ship Richard of Jamaica.[39] Luke Collingwood died three days after Zong reached Jamaica, two years before the legal proceedings that followed in 1783.[4]

Legal Proceedings

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William Murray, 1st Earl of Mansfield by John Singleton Copley, in his parliamentary robes as an earl
Wikimedia Commons

When news of the Zong massacre reached Great Britain, the ship’s owners claimed compensation from their insurers for the loss of the slaves. The insurers refused to honour the claim and the owners took them to court.[40] Zong‘s logbook went missing after the ship reached Jamaica, two years before the hearings started. Consequently the legal proceedings provide almost all the documentary evidence about the massacre, although there is no formal record of the first trial other than what is referred to in the subsequent appeals hearing.[41] The ship’s insurers claimed that the log had been deliberately destroyed, which the Gregson syndicate denied.[42]

Almost all the surviving source material is of questionable reliability. The two witnesses who gave evidence, Robert Stubbs and James Kelsall, were strongly motivated to exonerate themselves from blame.[b]Stubbs gave evidence in court; Kelsall produced an affidavit in the Exchequer proceedings initiated by the insurers.[43] It is possible that the figures concerning the number of people killed, the amount of water that remained on the ship and the distance beyond Jamaica that Zong had mistakenly sailed are inaccurate.[44]

First trial

Legal proceedings began when the insurers refused to compensate Zong‘s owners. The dispute was initially tried at the Guildhall in London on 6 March 1783, with the Lord Chief Justice, the Earl of Mansfield, overseeing the trial before a jury.[45] Mansfield had previously presided as the judge in Somersett’s Case in 1772, which concerned the legality of enslaving people in Britain. He had ruled that slavery had never been established by statute in Britain and was not supported by common law.[46]

Robert Stubbs was the only witness in the trial, and the jury found in favour of the owners, under an established protocol in maritime insurance that considered slaves as cargo.[47] On 19 March 1783, Olaudah Equiano, a former slave, told the anti-slave-trade activist Granville Sharp of the events aboard Zong, and a newspaper soon carried a lengthy account, reporting that the captain had ordered the slaves to be killed in three batches.[48][49] Sharp sought legal advice the following day about the possibility of prosecuting the crew for murder.[50]

King’s Bench appeal

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Granville Sharp, from a drawing by George Dance
Wikimedia Commons

The insurers applied to the Earl of Mansfield to have the previous verdict set aside, and for the case to be tried again.[51] A hearing was held at the Court of King’s Bench in Westminster Hall on 21–22 May 1783, before Mansfield and two other King’s Bench judges: Mr Justice Buller and Mr Justice Willes.[52] The Solicitor General, John Lee, appeared on behalf of the Zong‘s owners, as he had done previously in the Guildhall trial.[32] Granville Sharp was also in attendance, together with a secretary he had hired to make a written record of the proceedings.[53]

Summing up the verdict reached in the first trial, Mansfield said that the jury:

… had no doubt (though it shocks one very much) that the Case of Slaves was the same as if Horses had been thrown over board … The Question was, whether there was not an Absolute Necessity for throwing them over board to save the rest? The Jury were of opinion there was …[54][55]

Collingwood had died in 1781, and the only witness of the massacre to appear at Westminster Hall was again Robert Stubbs, although a written affidavit by first mate James Kelsall was made available to the lawyers.[56] Stubbs claimed that there was “an absolute Necessity for throwing over the Negroes”, because the crew feared all the slaves would die if they did not throw some into the sea. The insurers argued that Collingwood had made “a Blunder and Mistake” in sailing beyond Jamaica and that slaves had been killed so their owners could claim compensation.[57] They alleged that Collingwood did this because he did not want his first voyage as a slave ship captain to be unprofitable.[58]

John Lee argued that the slaves “perished just as a Cargo of Goods perished”, and were jettisoned for the greater good of the ship. The insurers’ legal team replied that Lee’s argument could never justify the killing of innocent people; each of the three addressed issues of humanity in the treatment of the slaves and said that the actions of Zong‘s crew were nothing less than murder. The historian James Walvin has argued that it is possible that Granville Sharp directly influenced the strategy of the insurers’ legal team.[59]

New evidence was presented that heavy rain had fallen on the ship on the second day of the killings, but still a third batch of slaves was killed. This led Mansfield to order another trial, because the rainfall meant that the killing of those people, after the water shortage had been eased, could not be justified in terms of the greater necessity of saving the ship and the rest of the slaves aboard.[55][60] One of the justices in attendance also said that this evidence invalidated the findings of the jury in the first trial, as the jury had heard testimony that the water shortage resulted from the poor condition of the ship, brought on by unforeseen maritime conditions, rather than from errors committed by its captain.[61] Mansfield concluded that the insurers were not liable for losses resulting from errors committed by Zong‘s crew.[55]

There is no evidence that another trial was held on this issue,[55][32] and despite Granville Sharp’s efforts, no member of the crew was prosecuted for murder.[62]

Effect on the abolitionist movement

Granville Sharp campaigned to raise awareness of the massacre, writing letters to newspapers, the Lords Commissioners of Admiralty and the Prime Minister, the Duke of Portland;[32][63] neither Portland nor the Admiralty replied.[63] Only one London newspaper reported the first Zong trial in March 1783,[64] the first public report of the massacre.[65] Little else about it appeared in print before 1787.[65][66]

Sharp’s efforts did meet with some success however. In April 1783, he sent an account of the massacre to William Dillwyn, a Quaker, who had asked to see evidence that was critical of the slave trade. The London Yearly Meeting of the Society of Friends decided shortly afterwards to begin campaigning against slavery, and a petition signed by 273 Quakers was submitted to parliament in July 1783.[63] Sharp also sent letters to Anglican bishops and clergy, and to those already sympathetic to the abolitionist cause.[67]

The immediate effect of the Zong massacre on public opinion was limited, demonstrating – as the historian of abolitionism Seymour Drescher has noted – the challenge that the early abolitionists faced.[66] Following Sharp’s efforts, the Zong massacre became an important topic in abolitionist literature and the massacre was discussed in works by Thomas Clarkson, Ottobah Cugoano, James Ramsay and John Newton.[48][65] These accounts often omitted the names of the ship and its captain, thereby creating, in the words of the historian Srividhya Swaminathan, “a portrait of abuse that could be mapped onto any ship in the Middle Passage”.[65][68] The Zong killings offered a powerful example of the horrors of the slave trade, stimulating the development of the abolitionist movement in Britain, which dramatically expanded in size and influence in the late 1780s.[80][88][89] In 1787, the Society for the Abolition of the Slave Trade was founded.[3]

Parliament received numerous petitions against the slave trade, and examined the issue in 1788. With strong support from Sir William Dolben, who had toured a slave ship, it passed the Slave Trade Act 1788 (Dolben’s Act), which was its first legislation to regulate the slave trade. The Act restricted the number of slaves that could be transported, to reduce problems of overcrowding and poor sanitation. Its renewal in 1794 included an amendment that limited the scope of insurance policies concerning slaves, rendering illegal such generalised phrases that promised to insure against “all other Perils, Losses, and Misfortunes”. [69] The Act had to be renewed annually, and Dolben led these efforts, speaking frequently to parliament in opposition to slavery.[70] It was not until the passage of the Slave Trade Act 1799 that these provisions were made permanent.[71]


a The number of deaths is unknown, but James Kelsall, Zong‘s first mate, later said that “the outside number of drowned amounted to 142 in the whole”.[2]
b Stubbs gave evidence in court; Kelsall produced an affidavit in the Exchequer proceedings initiated by the insurers.[43]



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