My day off and wouldn’t you know it, the rain’s bucketing down. I’m the only passenger on the number 22 bus trundling through the sodden hills of Scotland, on my way to visit some National Trust gardens. I’m sitting up chatting with the driver, Sylvan, who’s going to let me off at the right stop, but I can hardly understand a word he’s saying — his northern accent’s a killer.

I’m about to step out into the pelting rain, when he says it’s hardly a day for wandering round gardens. Instead he reaches down beside his seat and pulls out two bottles of Carib lager, cracks them open and I sit back to enjoy a two-dollar trip through a miniature, but today magnificently rainy, rainforest.

That bus ride was 10 years ago, but it’s been on my mind ever since — a book I’m writing came directly out of that first trip around the northern parishes of Scotland district, Barbados. And now, together with BBC producer and historian Louise Yeoman, I’ve been making a radio programme about Caribbean poor whites. In Barbados, they’re called “redlegs” because — according to legend — their ancestors in the cane fields got their legs sunburned below the hem of their kilts.

About 170 Jacobite rebels were “Barbado’ed” after the rising of 1715 — and there are other sources of Scots ancestry in Barbados, too. A few years after my bus ride with Sylvan I was back seeing friends and doing some research on the island. I met a man called Mac who looked as frazzled as a tourist halfway through a package tour out of Glasgow. The minute Mac spoke, however, the illusion was shattered: the man talked like Shaggy on drugs.

He lived in St Martin Bay, on the wild east coast of the island, up by the Scotland district, which rises into stark hills and craggy cliffs in the north of the island. It’s here that the redlegs have traditionally lived.

“Backras” Sylvan called them. “’Cause no respectable family wanted to sit next to poor white trash in church. They were made to sit in the back pews only.”

I’ve since heard other theories about poor white genealogy and lifestyles — and other translations of “backra”. According to Karl Watson of the University of the West Indies “nyam” buckras translates from an African language as “useless white men”.

These people are not the descendents of rich planters. Nor is their heritage confined to Jacobite rebels. They come from a rich stew of indentured workers from Scotland, Wales and northern England who were either exiled or sold themselves into slavery in the hope of making good eventually. There’ll be Barbado’ed Irish thieves and prostitutes in there somewhere, too. And Covenanters.

Louise, when I first told her the end of the story I knew — the West Indian side — immediately made the connection with the Covenanting wars. She contacted fellow historian Mark Jardine, who in the programme, takes us deep into religious Lanarkshire.

In a glen west of Douglas a man called James Gavin had been hiding out, but was caught by soldiers. In the wake of the rebellion by the Duke of Monmouth’s Covenanters the English army were nervy about any kind of Protestant agitator.

Gavin was a Cameronian — the most fundamentalist of Covenanting Protestants. He was marched, barefoot, to Edinburgh, where John Graham of Claverhouse, relentless pursuer of Covenanters, had the prisoner’s ears chopped off. He was then shipped out to Carolina, where he must have been bought by a Bajan planter.

Other Scots who followed had different roles. They were often factors and factotums — the men who held the whip. Gilbert Milroy, another Scottish Covenanter who became an overseer, was so violent that his slaves attempted to kill him.

The next wave of immigrants to make the appalling sail to the Caribbean was the starving poor. Scotland was in the grip of famine in the 1690s. Seven ships sailed out bearing 850 souls for Barbados. Then, 15 years or so later, the legendary Barbado’ed Jacobites followed them.

There were instances of white servants joining forces with black slaves in revolt against their masters. But they were rare, and died out once abolition and emancipation came onto the scene. Poor whites and freed blacks were now competing for the same jobs, the same slivers of land, the same crumbs of social status brushed from the planters’ tables. Poor whites, inevitably perhaps, played the race card.

For years the poor whites clung on to a sense of superiority: a romanticism of being lost Scots, waiting to return home in glory. That’s all changing now. Few people accept the tags “redleg” or “backra” any more.

There are still white and mixed race communities in parts of Bridgetown and around the Scotland area, but they feel, as Watson puts it, “black in a white skin”.

There are lost white tribes like the redlegs peppered around the Americas — supposed Poles in Haiti, semi-German communities in Jamaica. What is it that happens to a people who have been severed from their own history? None of the high principle of the Covenanting tradition seems to have stayed with Barbados’s poor whites; certainly no Jacobite nationalism. After clinging desperately to a forlorn take on white supremacy, they lost their music, their culture, and whatever little power they once had. The redlegs of Barbados and St Vincent are fast disappearing — like snow melting under the tropical sun. Poor whites.

Human Cargo is broadcast today on BBC Radio Scotland at 11.05am

Times Recommends

• Swine flu vaccine for all as drug rushed through
• Artificial sperm and the race to build a baby
• BBC jets out stars to tout for prizes