A section of a print of the Brookes Slave Ship diagram dated 1791 forms part of the collection in the Wilberforce House Museum in Hull, Britain, July 5, 2019. According to the museum the print is arguably one of the most recognisable images from the campaign to abolish the Transatlantic Slave Trade in Britain. The publication of this image provided the public with a clear visual representation of conditions on board slave ships for the first time. August 2019 marks 400 years since the slave trade to North America began. Picture taken July 5, 2019. REUTERS/Russell Boyce

An original slave chain that dates from the 18th century that was captured from a slave ship is seen on display at the Mobee Royal Family Slave Relics Museum in Badagry, Nigeria, June 20, 2019. This chain, which weighs about 80 Kg, was used to shackle about 20 slaves to both restrain them and group them together when working in the fields. August 2019 marks 400 years since the slave trade to North America began. Picture taken June 20, 2019. REUTERS/Afolabi Sotunde

A copy of a poster dated January 19, (year unconfirmed) advertising the sale of slaves by auctioneer Beard is seen on display at the Badagry Heritage Museum in Badagry, Nigeria June 20, 2019. The poster lists slaves of various ages, with different characters and skills and also includes the terms of sale. August 2019 marks 400 years since the slave trade to North America began. Picture taken June 20, 2019. REUTERS/Afolabi Sotunde

A copy of illustration Fig V on a document published in 1794 titled 'Remarks on the Methods of Procuring slaves with a short account of their Treatment in the West-Indies' that is held as part of the collection in the Wilberforce House Museum in Hull, Britain, July 5, 2019. The text under the image reads 'The husband and wife, after being sold to different purchasers, violently separated - probably never to see each other more!'. August 2019 marks 400 years since the slave trade to North America began. Picture taken July 5, 2019. REUTERS/Russell Boyce

Slave shackles dated from the period of slavery are displayed as part of the collection at the Museum of Civilizations of Ivory Coast in Abidjan, Ivory Coast, June 20, 2019. The shackles were used to restrain the feet of the slaves to keep them immobile during their transport in boats or when held in cells. They were acquired by the museum in 1942. August 2019 marks 400 years since the slave trade to North America began. Picture taken June 20, 2019. REUTERS/Luc Gnago

A detail from the painting 'A Liverpool Slave Ship' by artist William Jackson from around 1780 depicts a Liverpool slave ship moored off the coast of West Africa, is seen at the International Slavery Museum in Liverpool, Britain, July 24, 2019. Picture taken July 24, 2019. REUTERS/Phil Noble