BUNCE Island, just off the Sierra Leone coast in west Africa, stands as a symbol of Scotland’s forgotten role in the Atlantic slave trade. Few people in Scotland know of the island, but no-one in Sierra Leone is unaware of it. It looms in the national consciousness. In the 18th and 19th century, tens of thousands of Africans – ancestors to the men and women who now live in the capital of Freetown – were held captive there in appalling conditions by Scottish slavers, before being shipped across the sea to plantations in the Caribbean and the Americas.

Bunce Island was turned into a little oasis of all things Scottish by slavers. It had its own castle. It was leased from the local king who once a year would turn up to collect his commission dressed in a kilt. Isatu Smith, the head of museums and relics in Sierra Leone, describes how the Scottish slavers even built their own golf course on the island and dressed their slave caddies in tartan so they could be reminded of home. "They were serving Scottish masters, so they had to look the part," Smith says. "We have a shared history. It is very important that the Scottish people know about this – whether they accept it or not is another question."

READ MORE: Slavery museum to be set up in Glasgow

This week, Scotland will finally learn of the horrors of Bunce Island and be confronted by its forgotten role in the slave trade. David Hayman, the Scottish actor and director, has produced a new two-part documentary which begins on Tuesday night. In it, Hayman, through interviews with experts like Smith, lays bare just how central a role Scotland played in the slave trade.

The country was "up to its armpits in slavery", Hayman says, even though the nation has always presented itself not just as having little to do with the trade in human lives, but also a country which was a leading light when it came to abolition. It is a false history and one that Hayman is hell bent on correcting.

Scottish slavers ran Bunce Island from 1728 to 1807. They imported ice from Europe to keep food and wine cool in larders and enjoyed strolls in a private garden just metres away from pens where hundreds of human beings were kept like cattle before making the deadly Atlantic crossing. An estimated 50 per cent of slaves died on the journey. Eric Graham, a maritime historian, says that the dead were thrown overboard every morning. "All slave ships were followed by sharks," he says. "There was a dinner every day for the sharks."

The Atlantic slave trade saw goods from Britain – pots and pans, beads, alcohol, pipes, guns, knives, and cloth – traded for human beings in Africa. These slaves were then sold in America. The American cash was used to buy tobacco, sugar, cotton, rum and indigo which were then brought back to Britain. It was a trade that made merchants into millionaires.

Scotland in the 18th century was built on slavery. The Merchant City in Glasgow would not exist without the money that poured into the coffers of tobacco lords and cotton kings – who now have city streets named after them. These men were made rich beyond their wildest dreams by the profits of slavery. For the human beings traded as slaves existence was a living hell. Rape, murder, torture, abuse, humiliation and degradation almost beyond imagination, were the stuff of daily life. At least 12 million slaves survived being shipped across the Atlantic – with around 3.5m bought and sold by British slavers, among whom Scots stood out as the most efficient and enterprising.

READ MORE: Slavery museum to be set up in Glasgow

Celeste-Marie Bernier, professor of Black Studies at Edinburgh University, says: "Slavery bleeds in every building, in every brick, in every town across Scotland."

According to Hayman: "Scotland’s involvement in the slave trade is a story of uncomfortable truths over how we see ourselves and perhaps that is why it has been forgotten. It challenges the notion that we are all Jock Tamson’s bairns. Scots were plantation owners, slave owners, merchant ship owners. The profits fired Scotland’s industrial growth and in every city in our nation you will find civic buildings and private homes built from the profits of slavery – bricks drenched in blood."

There is now a growing campaign to, as Hayman puts it, "acknowledge our past" with an apology and reparations. There is also a campaign to establish a museum to slavery in Scotland, and for memorials and plaques to go up across the country on statues, streets and homes linked to slavery – such as the Gallery of Modern Art in Glasgow which was once the mansion of tobacco lord William Cunningham, a man made rich on the backs of slaves in the Americas.

Scotland: a canny wee nation when it comes to remembering

Professor Sir Tom Devine, the nation’s leading historian, says the scale of Scotland’s involvement in the slave trade is "truly mind boggling". He believes historians have a "sacred duty" to tell the truth about it, just as they have with "that other horror, the Holocaust".

Adebusola Debora Ramsay, of the Glasgow Slavery Legacy Tour which takes visitors around sites in the city linked to the trade, says that whenever the history of slavery is discussed in Scotland the nation appears to suffer from a "collective amnesia".

Poet Jackie Kay, Scotland’s Makar and a woman of Nigerian descent, once said: "Scotland is a canny wee nation when it comes to remembering and forgetting. The plantation owner never wears a kilt and Glasgow does not readily admit its history in a way that other cities have done." Liverpool has built a museum to its role in the slave trade and Bristol is in the middle of a long debate over what to do about statues to wealthy slavers in the city.

READ MORE: Slavery museum to be set up in Glasgow

Dr Stephen Mullen, an historian and author of the book "It Wisnae Us" about Scotland’s role, says Scots view slavery as a "peculiarly English problem", adding: "Scots have got off the hook." Slavery trickled down into every part of Scottish life – from the docker who brought sugar into the city, to the grocer who sold it, and the families who bought it to sweeten their tea. One major export from Scotland to the Americas was "slave cloth" to make cheap clothes for Africans on plantations. Salted herring from the Highlands had its main market in the islands of the West Indies as food for slaves.

The Jamaican-born scientist Sir Geoff Palmer, Professor Emeritus of Life Sciences at Heriot-Watt University, says if Bannockburn is in the history books, then slavery should be there as well. Scottish academic Michael Morris, an expert in slavery at Liverpool John Moores University, adds: "Scots like to promote themselves as part of the civilising mission of the British empire, so we glorify individuals like David Livingstone, and we would prefer to talk about our role in abolition rather than our role in chattel slavery."

Chris Dolan, the Scottish playwright who wrote an acclaimed novel about the slave trade called Redlegs, believes "we managed to forget about slavery for an awful long time. Now that we are waking up to the part we did play, it is very difficult for us as we have this mythology we tell ourselves that we are less racist people than other European nations, specifically England. That is not true. Therefore to wake up and find we are involved in slavery as much as other parts of Europe is difficult."

As David Alston, an historian who is now chair of the board of NHS Highland, sees it Scotland’s own historic grievances hold us back when it comes to confronting the past – specifically events such as the Highland Clearances. "We want to tell ourselves a story that in the Highlands we were victims," he says, "but if you want to portray yourself as a victim the last thing you want to do is be the victimiser."

In Jamaica there are thousands of Campbells named after the Scots who owned their ancestors

One need only look through the records of wealthy Scots to find clues which were always staring us in the face over our shameful past. Just look at the ledgers of Sir Robert Cunningham, a slave owner on St Kitts. In a record from 1730 he lists his horses – Jack, Beauty, Trooper, Duke – and a few pages later, his slaves: Aberdeen, Glasgow, Edinburgh, and Whisky, a blacksmith aged 23 and worth £75.

One of the reasons that it has become easy to forget the past is that we helped destroy it. When Sierra Leone achieved its independence in the 1960s, the departing British took all records of slavery with them.

Joannes Caulker, an historic archivist in Freetown, says: "We lost our history. They only let us know what they wanted us to know." Joe Alie, Professor of History at Sierra Leone University, is clear that his country is still paying the price of slavery. Millions of young men and women were taken away, robbing the country of human potential, and forced to slave for white masters. "While we lost, they gained," Alie says. He speaks of an inferiority complex in nations subjected to slavery. "We were dehumanised during the slave trade era – that is a lasting legacy."

READ MORE: Slavery museum to be set up in Glasgow

Hayman also journeyed to Jamaica with Graham Campbell, a well known figure in Glasgow with his rasta dreadlocks, and now an SNP councillor in the city. Speaking of the rape of African women by white masters he says that is what "created people with Scottish names like me".

In the Jamaican phone book there are literally thousands of Campbells – page after page of them – all named after the plantation owner who once bought their ancestors. The book is also full of Mackenzies, Macleans, McLeods and McPhersons. Scotland and its trade in slaves shaped the modern island. "I have this name because you were over there," says Campbell. "I am the descendant of survivors."

On Jamaica there stands a plantation once run by the Stirling Maxwell family, who owned Pollok House in Glasgow, now a national treasure. The plantation was called Hampden. It had more than 200 slaves. The national costume of Jamaica, the quadrille dress, is tartan. The St Andrew’s Cross is in the Jamaican flag. The dock in Jamaica where barely alive slaves were taken from ships before being washed, oiled, shaved and given rum so they would appear in good health for the slave market is called Farquharson’s Wharf – it was run by Scots.

Further south, in British Guyana, a run of coastal towns is testament to how entrenched Scots were in the slave trade there. The towns all have highland names – Belladrum, Cromarty, Dingwall, Dunrobin, Golspie, Inverness. The list goes on and on.

A legacy in blood, bricks and mortar: Scotland’s shrines to ill-gotten wealth

Back across the sea in Ayrshire, the stately home of Auchincruive stands as a "colossal shrine to ill gotten wealth", says Hayman. The house was built by Richard Oswald, a merchant slave trader who was an investor in Bunce Island. Oswald owned four plantations in the Caribbean and left a fortune worth £40m.

In Clarkston, on the outskirts of Glasgow, stands another National Trust of Scotland jewel, Greenbank Gardens, once owned by Robert Allason. He and his two brothers had the slave trade sown up. Goods would go from Robert in Glasgow to a brother in Africa to be exchanged for slaves, and then another brother with a plantation in Virginia would pick up the slaves and send tobacco back to Scotland. It was a money machine, with human lives oiling the engines.

One of Scotland’s most powerful slavers was John Gladstone of Leith – the father of William Gladstone who became one of Britain’s most famous prime ministers. When Britain finally abolished slavery in 1833 slave owners received millions in compensation which they went on to invest in industries like banking, mills, mining, and railways. John Gladstone had 2508 slaves for which he was paid a sum worth £83m in today’s money.

Jean Francois Manicom, curator of Liverpool’s International Slavery Museum, tells a story of an anonymous donor from Edinburgh, who he describes as a Scottish superhero. Once every fortnight the donor posts a Scottish ten pound note to the museum with an apology on behalf of the nation. "This is very symbolic," says Manicom, "a very powerful story of reparation."

Another Liverpool historian, Lawrence Westgaph, himself a descendant of slaves and slave traders, believes that the racism which blights the UK today has its roots in the slave trade. "Racism comes down to the idea that some people are less human than others and slavery helped codify that. What I see today is that anti-black racism has its origins in the slave trade.’" Confronting the past, helps draw the poison.

How does Scotland confront its past? Apology? Reparations? A memorial?

So how does Scotland deal with the dreadful legacy of slavery? Historian David Alston says, "acknowledging the past is the first step – it is only after that can you get on to the questions of reparations". Geoff Palmer says that what would repair the wrongs of the past is a "country which is wealthier contributing to a country that helped make that wealth".

So apology and then some form of compensation are now coming front and centre among those thinking about how Scotland’s deals with its past. Graham Campbell wants to see schools and colleges in Scotland and Jamaica link up through student exchanges, for business connections to be forged – real concrete steps that will help improve education and lives in Jamaica, a country still living with the effects of slavery nearly 200 years after abolition.

For Hayman there is no going back and no hiding place. "We rewrote history to make ourselves look the good guys for abolishing slavery while blaming everyone else – well now is the time for truth."

He adds, "I like to think I live in a modern Scotland that is open-minded, free-thinking, liberal, tolerant, warm and friendly. Scots are loved the world over, but less than five generations ago our ancestors helped create and sustain crimes against humanity on an industrial scale simply to get stinking rich. This is an uncomfortable truth, but hopefully we can now find the courage and dignity to say we are sorry."

Slavery: Scotland’s hidden shame begins at 9pm on BBC 2 on Tuesday, November 6