HER name was Janet Schaw, and she was the daughter of a family of gentlemen farmers near Edinburgh. In 1775 she found herself on the Caribbean island of St Kitts, where she witnessed the conditions endured by African slaves who had the wretched misfortune to work on sugar plantations.

Every 10 slaves had a driver, who was equipped with both a long and a short whip. The slaves, men and women alike, were naked "down to the girdle", so that Schaw was able to see the whip-marks gouged on their flesh.

In her letters she wrote that that while "humane Europeans" would be appalled by such treatment, such reactions were in her opinion misconceived. “When one becomes better acquainted with the nature of the negroes,” she wrote, “the horrour [sic] of it must wear off. It is the suffering of the human mind that constitutes the greatest misery of punishment, but with them it is merely corporal. As to the brutes it inflicts no wound on their mind, whose Natures seem made to bear it and whose sufferings are not attended with shame or pain beyond the present.”

But this was an era when the Caribbean was known, with very good reason, as a slaves’ graveyard. Before they even arrived there, the slaves had to endure appalling conditions on the voyage from Africa. In 1789, anti-slavery campaigner William Wilberforce estimated that 12 per cent of them died on the long journey; another 5 per cent died when they were seized from their homes, force-marched to the coast and incarcerated before being put on to grossly overcrowded ships.

What awaited them in the Caribbean was chattel slavery. They remained the property of their owners until they died. Children born to enslaved women became the masters’ property, too, either to be sold on, or worked on the plantations where they had been born. Any slave who dared rebel, or tried to escape, was punished with an astonishing brutality.

For long decades, Scotland denied it had any role in such an inhumane trade. Academic neglect was mingled with public amnesia. We preferred to remember instead how Scots played an important role in the campaign to abolish slavery.

But a series of articles since 2000 has chipped away at that lie. And now comes the first dedicated scholarly book by Professor Sir Tom Devine on the subject, an authoritative volume that demolishes it completely.

Scotland, it says, was knee-deep in two transatlantic colonial systems that relied on slavery – the tobacco plantations of Virginia, Maryland and North Carolina, especially before 1776, and the West Indies sugar plantations, which after 1783 assumed a major role in the Scottish economy. Moreover, every part of Scotland was involved.

A few words from the book’s foreword will suffice here. Scots, writes Professor Philip D Morgan, the current doyen of Caribbean historians, “owned and managed enslaved people in many New World slave societies, from Maryland to Trinidad, from St Croix to St Kitts … The scale of Scottish involvement in the slave economies and societies of the New World was … wide and deep.”

“I’ve been writing history since the early 1970s,” says Devine, “and the research process in this book, and the results, have been more remarkable than any other project I have been involved in, in terms of breaking through an established orthodoxy, and painting a picture which is almost the reverse of what most people believed up until the year 2000. In terms of intellectual excitement, it has been fascinating.”

Scotland’s most prominent historian is editor of, and a contributor to, Recovering Scotland’s Slavery Past: The Caribbean Connection, which, armed with the fruits of considerable archival research, corrects the myth about Scots and slavery. Devine and his nine co-authors see it as an important educational tool.

“This is a huge area of Scottish history which has been completely marginalised and indeed forgotten,” he says. “There has been a collective national amnesia about slavery. In 2001 a major study of Scottish history, The Oxford Companion to Scottish History, hardly makes a reference to this. It had only one allusion to the West Indies, and this was in the context of the sale of coarse linens.

“The understanding about Scotland and slavery has only started to happen in the last 10-15 years, and the reason why it’s important is because the past makes us as a people and individuals. Despite the fact this might be regarded by some as a negative or darker aspect of the Scottish past, it has to be built in to the overall picture alongside the more positive contributions that the nation has made globally.

“One of the things that comes out in one of the chapters is that the narrative about slavery in Scotland until recently has been about the honourable Scottish role in abolition. But that leaves aside the reality of what happened.”

Many are the factors behind this amnesia. One of them concerns the relatively low number of slaves who were shipped from Africa to Chesapeake tobacco plantations or Caribbean sugar plantations by ships that sailed from Scottish ports such as Port Glasgow. Between the opening decades of the 17th century and 1807, when the British slave trade was abolished, ships of the Empire took 3.4 million Africans to a life of servitude. Research suggests, however, that only 4,500 Africans were on ships that actually embarked from Scotland and sailed across the Atlantic via Africa.

“But the Scottish role, in a sense, was indirect,” says Devine. “Many Scottish merchants, skippers and surgeons migrated to English ports and were very active there.

“Secondly, Scots who were actually in the Caribbean were highly active in the direct slave trade from West Africa to the West Indies. And of course the whole economic system of both the Caribbean and the North American tobacco colonies would have been impossible without unfree labour.

“Despite the minuscule evidence of direct trading, the evidence in the book argues that it might well be that in relation to population size, the Scottish involvement in the entire slavery system was greater even than that of England. It was certainly much greater than that of Ireland or Wales.

“But there is an argument that comes through in some of the chapters that when you look at the Scottish role in relation to the population size of Scotland compared to England, then the Scottish role was disproportionate. That is quite a remarkable research finding."

At the height of the slave trade, one-fifth of the ship's captains and two-thirds of the surgeons who manned slave-ships out of Liverpool were Scottish. There are many more details like this, equally telling, in the book's pages, including the high levels of compensation paid to Scottish merchants for the losses of their "property" when slavery was finally abolished in the Empire in 1833.

One chapter, Did Slavery Make Scotia Great?, argues that markets and capital from the Atlantic slave-based economies helped fuel the Scottish industrial and agricultural revolutions and so create the Scotland of today.

It is also the case that Scottish investment and involvement in slavery extended far beyond Glasgow. “In terms of slave ownership it was everywhere," says Devine. "In the last phase of slavery, in British Guiana, on the mainland of South America, the major Scottish demographic were Highlanders and people from the north of Scotland. That was the last profitable slave colony: individual owners who had capital in slaves there actually received higher compensation than in the rest of the Caribbean area.”

Glasgow’s links are better known. Stephen Mullen, who contributes to this research, detailed them in his 2009 book, It Wisnae Us.

One of the most notorious figures is Richard Oswald, who worked for his cousins’ Glasgow-based merchants’ firm before, in London in 1743, setting up his own company, working in tobacco and then in slaves, horses and sugar.

“He made a lot of money during the American War of Independence, selling munitions, but one of his major sources of wealth was the establishment of a slave ‘fort’ on Bance Island, off the coast of Sierra Leone. During that fort’s period of activity, we reckon that 30,000 Africans were exported from it to the Caribbean.

“There was actually a small golf course on it as well. Legend had it that the caddies were slaves who were dressed with tartan breech-pouches around the private parts.

“Having made money out of slavery and arms contracting, then retired to Auchincruive, in Ayrshire, where the agricultural college now is. He also had an estate at Cavens, in Kircudbrightshire. It was a classic pattern: you made your money and you bought into land, which gave you security and prestige. It was a passive source of income, which came from tenants paying rent.” The Oswalds have a family burial plot in Glasgow Cathedral, though Richard himself is buried in the grounds of a parish church in Ayrshire.

Sir James Stirling of Keir (1740-1805) owned slaves and plantations in Jamaica. Andrew Cochrane of Brighouse (1693-1777) was a Tobacco Lord who also served as a Lord Provost of Glasgow.

Many parts of modern-day Glasgow carry echoes of merchants who were associated with the tobacco business or the Caribbean sugar business, both of which were utterly dependent upon the enslavement of black people: Jamaica Street, Buchanan Street, Virginia Street, Glassford Street, Ingram Street, Tobago Street. The Gallery of Modern Art began life as a mansion constructed for William Cunninghame of Lainshaw, a Glasgow merchant implicated in the Virginia tobacco trade and the West Indies sugar business. The magnificent church of St Andrews in the Square was funded by colonial merchants.

The Kingston Bridge, too: Kingston, of course, is the capital of Jamaica, and refers to the former Kingston dock on the Clyde. Other examples can be found across Scotland.

“One of the reasons that merchants’ involvement in slavery was forgotten about," says Devine, "was that many of the individuals concerned were at the very highest level of Glasgow society – they were called the sugar aristocracy or the Tobacco Lords. The Victorian books about them were all laudatory – to their authors, they were the mercantile heroes who made Glasgow. Not a mention at all about the slave system on which these economies were based. It’s fascinating, because by that time Scotland was a really passionate anti-slavery society, with David Livingstone being seen as the great Protestant saint who was trying to destroy slavery in Africa.

“But this local situation – the stain on the Scottish character, if you like – no reference was made to it at all.”

There was, however, the interesting case of James Ewing (1775-1853), a wealthy Glasgow merchant. One obituary observed that Ewing had been “apparently disliked by some because of his connection with slaves in the Caribbean”. Nevertheless, this had not been enough during his lifetime to prevent Ewing from becoming an MP, chairman of Glasgow Chamber of Commerce and Lord Provost – not to mention the grateful recipient of an honorary degree from Glasgow University.

Did any merchants express contrition for what they had done? “No,” says Devine. “All you get is silence, really. Up until about the 1770s silence could be expected, because there was hardly any criticism of chattel slavery until then. But then, of course, you get the huge movement towards abolitionism.”

Is Scotland, having finally been shaken from its denial about slavery, now ready to accept what really happened, that their ancestors traded in human misery? “I just hope we are now a more mature democracy, not least because we went through the remarkable process of the referendum last year. I think that Scotland will now be willing to look at this.

“If we had tried to publish this book in the 1960s or 1970s, where there was a strong Scottish sense of victimhood, it would have been a different story. In 1967, you’ll remember, we were given that dirge, Flower of Scotland, by the Corries. That was the time, too, when John Prebble was making a lot of money out of victimhood studies of the Scottish Highlands. This is one of the reasons why historians of that time were not really focused on slavery, because the whole dynamic of enquiry was quite different.

“Certainly in terms of the public presentations we’ve done in relation to the book, over the last six months to a year, the audience response is, ‘Why weren’t we told about this before?’, and also that this is completely fascinating. I haven’t come across any evidence of hostility.”

Does Devine think an apology might be due from Scotland for its role in chattel slavery? “That’s an issue for politicians,” he says. “My trade is really to describe why things happened, and what happened. One of the great historians of an older generation, GR Elton, used to say the historian can’t be a hanging judge. The argument is that people in the past had different values. We who are living in 2015 don’t have any direct responsibility for what happened.

“What I would like to see, however – because there is no doubt that chattel slavery damaged Caribbean society – one possible way forward would be to establish tighter relationships, especially in education, with the Caribbean. And if there’s going to be another Homecoming Day, there should be a special invitation to the Caribbean. The Kingston telephone directory is packed with Scottish names.”

Recovering Scotland’s Slavery Past is no mere dry, academic book. Here and there you come across passages that speak to you directly and remind you of the sadistic treatment meted out to the slaves who were worked to death on sugar plantations.

One observer noted that the punishment for slaves who tried to rebel involved them being “nail[ed] down on the ground with crooked Sticks on every Limb then applying the Fire by degrees from the Feet and Hands, burning them gradually up to the Head, whereby their pains are Extravagant”.

Devine gingerly volunteers details of one particularly ghastly punishment. “This is from the diary of one Thomas Thistlewood, a plantation owner from Lincolnshire. One of his techniques was to have the guilty slave pinned to the ground with his mouth wide open. Someone else would defecate into the man’s mouth, which would then be sewn shut for three days.

“Because, you see, they regarded these people as not human. When you look at the inventories of slave ownership, on the one page you’d have human beings and on the next page you’d have cattle, because they were just regarded as such. Like livestock.”

Recovering Scotland's Slavery Past: The Caribbean Connection is published by Edinburgh University Press, priced £19.99. It will be launched at an event at Trades Hall, Glassford Street, Glasgow, on October 22 at 6.30pm.