Discover the reality of Ross Poldark's life and times at Danescombe Mine

Cornwall was for centuries an end-of-the-line sort of a county, poor and remote with little going for it. While East Anglia boomed through the Middle Ages with wealth from the wool trade, Cornwall was a backwater. This was not because it didn't have rich natural resources – there were endless seams of valuable copper beneath the surface – but because it was impossible to extract the metal on any scale without the tunnels filling with water.

Then in 1712 Thomas Newcomen, a tool salesman from Devon, unveiled his new invention: "a fire machine for drawing water from the mines". His contraption, which used steam in a cylinder to propel a piston, was the first true steam engine and would change the world.

The creation of the steam or "Newcomen" engine, designed to pump water out of copper mines, transformed Cornwall's fortunes. Landowners who had for hundreds of years earned little from their rough acres were suddenly able to get at the priceless tracts of copper beneath their lands. By the time of Ross Poldark's story, the 1780s, around one hundred distinctive tall stone engine houses had sprung up across Cornwall.

Stay in a cottage in Poldark country with Radio Times Travel

Danescombe Mine, which has a similar tall engine house, stands in the Tamar valley on the south side of Cornwall, and was built on the Cothele estate. It was commissioned by the Edgcumbes, an ancient Cornish family who found new wealth with the sudden explosion in the copper mining industry. In 1789, King George III and Queen Charlotte visited the gregarious Richard Edgcumbe – who chanced much of his family's new money on the gaming tables of London – at Cothele, and he was given an earldom.

While the Earls of Mount Edgcumbe, as they now were, enjoyed their renewed wealth, life in the copper mines was hard and hazardous. Half of Cornwall's thousands of miners were very young men, aged between 15 an 25. The work was dangerous, with numerous deaths – a quarter of the men never reached 30.

As well as hauling the minerals up from the ground, the mine workers operated the huge machines that crushed and ground them – also powered from the engine house. The crushed minerals were then taken down the Tamar river to a smelting works to be roasted and smelted to burn off impurities. This had to be done where there was lots of coal, and scores of smelting works were established in south Wales. Here Cornish tin was made ready for pipes and pans, and the new British copper coinage was (and still is) minted.

But the wealth that was created by the Cornish copper rush was to go almost as fast as it came. Ironically it was the steam engine that was responsible for both. With the creation of large-scale steam ships that could cross the Atlantic at speed, it was soon economic to import vast quantities of copper from South America. The result was a dramatic collapse of the British copper industry. By the middle of the 19th century, copper production in Cornwall has shrunk to a quarter of its former size.

Choose from hundreds of Cornish cottages with Radio Times Travel

Danescombe was among the scores of mines then that were closed, and in 1872 its machinery was sold off. The 6th Earl of Mount Edgcumbe made an inheritance tax deal with the Treasury, and the runs of Danescombe came with it.

The Landmark Trust first visited Danescombe Mine in the early 1970s, and it was an incredibly sad sight. The roof had collapsed, the engine house was derelict, the machinery and internal fittings had all gone. It was ruinous and swathed in foliage and ivory.

The Landmark Trust took a long lease on Danescombe Mine from its new owners, the National Trust. We then undertook a massive restoration project. It would be one of the earliest conversions of an industrial building into a house – the beginnings of a model that would provide a lifeline for hundreds of buildings across the country.

The result is a wonderful hybrid, an engine/house. Like all our buildings, it is let for holidays to provide enough income for us to maintain it. The top floor, where the beam of the engine once pounded up and down, is now a bedroom where visitors can dream of Cornwall in days of yore – knowing that this fascinating part of its past has been saved.

Find everything from romantic cottages to fabulous accommodation sleeping 20+ people with Radio Times Travel

Restoring Britain's Landmarks continues on Wednesday on Channel 4 at 8pm. The Danescombe Mill episode is available to watch on All4.

To order Landmark: A History of Britain in 50 buildings for £22.50 (normally £25) including p&p, visit Radio Times bookshop

Where is Poldark filmed? Cornwall, Bristol and London Location guide