There's a story David Hayman heard when researching a BBC documentary about Scotland's links to the transatlantic slave trade that didn't make the final cut.

It tells of the wife of a prominent Scottish slaver travelling to visit her husband's plantation on a ship carrying human cargo. On deck when the enslaved Africans were brought up for their daily flogging and meagre water supplies, she was irritated by the cries of an infant who she promptly had thrown overboard.

True or not, the story is no less horrifying than the myriad of recorded instances of abuse and murder subjected on stolen people sent across the seas to lives of servitude.

On Sunday, the actor and director's documentary, Slavery: Scotland's Hidden Shame, will be screened on BBC Scotland at 9pm, two years after its debut, at a time, he says, when the country, and the world, is reassessing its attitudes.

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He said: "Scotland's involvement has never been recognised in popular culture but it's an important issue because until we come to terms with our slave trading past, we can't take on today's racism.

"We have to go into the future with the confidence of owning our past."

The two-part examination of Scotland's culpability in the lucrative trade travels from west Africa to the Caribbean and the slaving ports of Port Glasgow, Greenock and Aberdeen.

Particularly confronting, was Mr Hayman's visit to Bunce Island, off the coast of Sierra Leone. It is a tiny island that looms large in the history of slavery in west Africa, for it was from here that tens of thousands of souls were sent in slaving ships to the Americas and West Indies.

Many of the major figures were Scots at this, one of the key slave trading stations, where enslaved people were held for up to three months before transportation.

Traders and their families relaxed under the shade of fruit trees in decorative gardens on the island overlooking the holding pens separating the African men and women imprisoned there.

Mr Hayman said: "My visit to Bunce island was shocking, it's so small but the scene of such brutality and man's inhumanity to man on such a large scale. There's a sad, brutal melancholy there and it's extraordinary [the British] drank gin and played golf there.

"We were the gang masters who ran the plantations. We went there with a bible in one hand and bullwhip in the other - god fearing people who didn't see black people as human."

Real change can't come, Mr Hayman believes, until Scotland's role in a bitter and brutal colonial history is acknowledged.

He said: "The timing of showing the documentary again couldn't be better as now there's this very fierce and passionate public debate going on about racism and slavery which is so healthy.

"Throughout the years there have been moments like this. I believe there's something different about this. It's taken the death of one man and the shockwaves of George Floyd's death have been like a tsunami. It was so spontaneous that this feels like it could be a real turning point."

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Discussions on pulling down statues of slavers and renaming the streets of Edinburgh and Glasgow are "tricky" for the Glasgow-born broadcaster who supports calls for adding information to the monuments.

"We shouldn't erase our history. We should add plaques that state boldly what these men were responsible for, the number of slaves they owned, the carnage they created and how Scotland benefitted from this.

"It's extraordinary if you think there are white people walking round Scotland today unaware of their links to slavery - some will be descendants of black slaves and white slavers - it is a wicked irony that the nations are interlinked."

He is an ardent supporter of the campaign run by the Coalition of Race Equality and Rights to establish a national museum in Glasgow dedicated to illuminating Scotland’s role in empire, colonialism, slavery and migration and hopes the current discourse will drive it forward.

"We've said 'it wisnae us' but the truth is we ran the five biggest slave companies out of Liverpool. We went to London and set up banks and insurance companies that provided credit for the plantations.

"The profits from Scotland's involvement are what the two mighty empires of Britain and the United States of America are built on."