The iron industry in Merthyr Tydfil was founded by a slave trader called Anthony Bacon.
Bacon grew rich on the slave based economy of the Atlantic world. In the 17th century there was a huge array of trades and industries which were based on the vast fortunes flowing out of the sugar estates in the Caribbean.
He made his money as a merchant trading in slave produced tobacco and he was also an important government contractor.
His contracts included supplying food to troops guarding slave forts on the African coast. And he provided "seasoned and able working Negroes" for government works on Caribbean sugar islands. He was paid a monthly fee for these slaves, which stopped if they died or ran away.
"Every aspect of his life touches upon slavery in one way or another. His early life as a tobacco trader, and his later life as a government contractor," says Dr Chris Evans of the University of Glamorgan.
Bacon was already an important and rich merchant when he came to Merthyr. He used some of his money to build the Cyfarthfa Ironworks at Merthyr in 1765 and develop infrastructure, like the first road link between Merthyr and Cardiff.
Dr Evans says Bacon turned Cyfarthfa into the most important centre for gun founding in Britain (see the cannon pictured above outside Cyfarthfa Castle).
He says the slave trade did not only provide the money to set up the works - the slave based wealth of the Caribbean was important in providing markets for the guns.
"Bacon's principal business is supplying cannon to the Royal Navy, and the Royal Navy's principal business, after the defence of the British Isles themselves, is to patrol sea lanes and to look after the West Indies, the most valuable colonial possession that the British have at that time.
"And that is something that is deeply dependent on the slave business," he told the BBC Wales TV programme Wales and Slavery: The Untold Story.
Slave ships also needed to be armed in the dangerous world of the 18th century.
"If he was anything like other gun founders at the time he would also have supplied cannon to private traders, to merchants in places like Bristol or Liverpool," said Dr Evans.
The demand for guns was not the only link between slavery and the iron industry.
Iron bars - known as "voyage iron" were used as a kind of currency on the coast of Africa and could be traded for slaves by merchants.
"We know from the records of the Royal Africa Company in the late 17th century precisely what the exchange rate was in particular places. Twelve iron bars buys you an adult male slave," Dr Evans told the programme.
The sugar estates themselves - which were worked by enslaved Africans - needed iron for agricultural equipment and even shackles and implements of torture.
Records show that iron from the Dowlais Ironworks in Merthyr were used to make sugar crushing rollers for Caribbean slave plantations.
The links between the iron industry and slavery are an example of the economic importance of the slave-based Atlantic economy to Britain at the time. Dr Evans says that slave based economic system had an important impact on the way Wales became an industrial nation.
"British mercantile life was dominated by slavery. One way or another the Welsh economy is intimately connected and directly connected with the slave system as a whole," he said.
He says the industrial revolution would have happened without slavery and the slave trade but it would have happened in a different way and at a different pace.
Another slave-based venture which Bacon got involved in was the "Dismal Swamp Company".
He was a partner of the future US president George Washington in this venture to drain and log a vast swamp and use it for hemp production. The hard work would, of course, be done by the forced labour of enslaved Africans.
Records in the US show that Bacon gave ten slaves to the venture. Harry, the most valuable was listed as being worth £75 - Hannah, "a girl" was valued at £37.10. The venture failed.
Bacon died in 1786, and the Cyfarthfa ironworks were taken over by Richard Crawshay, who he'd brought in as a partner.
The plant continued to prosper under the Crawshay family until the iron industry was superceded by steel.
The ironworks closed in 1874, later re-opening as a steel plant before closing for the last time in 1919.
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