Two stories, usually seen as disconnected, unfold themselves during the second half of the 18th century. The first is the increased dominance of Britain in the transatlantic slave trade. According to estimates from the Slave Voyages database, the number of enslaved people carried by British ships more than doubled, from around 410,000 in the first quarter of the century to more than 830,000 in the third. The second is the establishment of William Shakespeare as the national bard. As scholar Gary Taylor puts it, “Shakespeare’s coronation as the King of English poets” dates from the third quarter of the 18th century, boosted by the actor David Garrick’s lavish Shakespeare Jubilee celebrations in Stratford-upon-Avon in 1769.

These stories have their meeting point in one specific object: the valuable book known as Shakespeare’s First Folio, published 400 years ago in 1623. And the history of this book also contributes to ongoing debates about what happened to the vast profits made from the trade and exploitation of enslaved peoples in the late 18th century and beyond.

In his landmark study Capitalism and Slavery in the 1940s, the Trinidadian historian Eric Williams argued that the slave economy pump-primed Britain’s Industrial Revolution (and that it was the development of alternative sources of profit through manufacture, rather than moral concerns, that motivated abolition). For other commentators, plantation profits fuelled extravagant spending and conspicuous consumption among the Georgian gentry. The luxury goods market – in Wedgwood porcelain, in Chippendale furniture, and in valuable books – was stimulated by increased wealth derived from enslaved Africans.

We tend to celebrate the First Folio, and, indeed, without this book, half of Shakespeare’s plays would have been lost, and without them, Shakespeare would not be a global cultural figure. But in addition to its cultural or artistic value, copies of this book have increased significantly in financial value.

At its original publication, this book cost £1, or the equivalent of several years of cheap theatre-going at a penny a pop. The earliest buyers were high-status men: a bishop, a young Kentish gentleman, a nobleman. It was a good investment. After a slow start, prices began to rise significantly in the mid-18th century. Editors and scholars were rediscovering this as the most authoritative text of the plays (not, as had long been thought, the 1685 or Fourth Folio), and the book was reframed as a significant classic. The notable bibliophile the Duke of Roxburghe paid an outlandish sum for a copy in 1790, firing the gun on a price race that has continued unabated. The most recent copy to sell at public auction reached almost $10m.

That particular record-breaking copy brings together the economy of enslaved people and the increasing status of Shakespeare. It was sold at Christie’s in New York by Mills, a private college in California, which was suffering financial difficulties, but it had previously belonged to the eccentric MP and Sussex landowner, John Fuller. Fuller – who wanted to be known as “Honest John” but couldn’t escape the nickname “Mad Jack” – inherited the Rose Hill estate at Brightling in Sussex and two Jamaican plantations, including more than 250 enslaved people from his uncle. He, and his lifestyle – which included his patronage of JMW Turner and his purchase of a new copy of the 1623 First Folio – were directly funded by enslaved labour. A half-hearted parliamentarian on most issues, Fuller used his voice most extensively as an outspoken anti-abolitionist, sneering at length in the House of Commons about the absurdity of the idea that “we should give up the benefit of the West Indies on account of the supposed hardships of the negro”.

In the first years of the 19th century, then, Jack Fuller fought the East Sussex parliamentary election while his Whig opponent chose to focus on his anti-abolitionism. One of the anti-Fuller campaign posters mocks plantation advertisements in unflinching terms: “WANTED, For immediate service in the West Indies, about one thousand NEGRO DRIVERS, though none need apply but men who are muscular – who can lacerate the back of a Black to the bone at every infliction of the lash, and who have the courage to continue the stripes though his object should be writhing in the agonies of death”. It just won’t do to argue that the standards of the present should not be imposed on the past: Fuller’s support for slavery was recognised at the time as excessive, dehumanising and immoral.

At precisely the same time as this election, Fuller was getting his hands on a trophy book: the 1623 First Folio. In correspondence with the most important Shakespearean of the age, the Irish editor Edmond Malone, Fuller was reassured that his was an authentic and fine copy. This was a world where anything, including humans, could be bought at a price. Just as we are undertaking a reckoning with the colonial underpinnings of the countryside, we need to follow the money behind valuable books – even our beloved Shakespeare. The history of the First Folio is a history of Shakespeare’s genius, but it also has a darker history of money, power, and inequality.

• Shakespeare’s First Folio: Four Centuries of an Iconic Book by Emma Smith is published by Oxford University Press (£20)