A pillar of sunshine moved across the cliff face, highlighting an arch of blue oxidised copper. My companion, Hetty, smiled at my amazement: there are plenty more seams like this, she said.
In the waters just beneath, a seal popped up, looked about and, as if similarly nonchalant about the band of copper, smoothly disappeared. From my vantage point above Trevaunance Cove I gazed down in hope of spotting it again, then stretched my eyes up to the mine buildings dramatically punctuating the inland horizon.
Seal colonies developed after the mines in the district closed down, Hetty explained. She runs kayaking tours here and often sees seals in the caves, swimming below the remnants of old shafts. Energetic winds had thwarted our kayaking plans that day, so instead we were taking a spectacular walk around St Agnes, on Cornwall's northern coast. Hetty was keen to share insights about the area, particularly its remarkable industrial heritage. The mines, she said, followed seams of copper and tin inland and under the sea, with tunnels kept relatively free of water by steam pump engines, developed in the early 19th century.
In the wake of the remade Poldark television drama series, I had come to Cornwall to revel in the landscape. Winston Graham wrote the first of his tales about the tin-mining Poldark dynasty in a beach hut at Perranporth, just around the coast from St Agnes. Back in the 1970s his novels became one of the most successful small-screen dramas ever, attracting an audience of some 15 million, of which I was one. I put it down to giddy youthfulness that while I followed the saga of Ross and Demelza, the mining aspect of the story passed me by. It won't this time around — in exploring Poldark country I became increasingly intrigued by Cornwall's industrial legacy.
My first stop was Poldark Mine, originally called Wheal Roots. It lies north of Helston in the Wendron Valley, where a staggering 640 mining concerns are recorded in parish records. Like many other such workings, Wheal Roots became a "lost" mine after the 1860s (they say gardening in this region comes with the occupational hazard of the sudden shafts you might uncover). This mine was rediscovered in the 1970s, developed into a visitor attraction and, with permission from Graham, was cleverly renamed Poldark Mine, which contributed to its post-industrial success.
Latterly, though, it fell on hard times. It was acquired in May by retired businessman David Edwards, who is set to transform its fortunes. His timing was perfect: the mine became one of the settings of the new series. Its strength, both as a tourist attraction and a film location, is that you can access the tunnels, descending nearly 50m. I emerged humbled by the hardship the workers endured and amazed by tales of the extent to which mining became part of the Cornish DNA.
"They say that wherever in the world you find a hole in the ground, there will be a Cornishman at the bottom," said my guide Alan, alluding to the fact that in the 19th-century Cornish miners took their expertise to Australia, South America, Mexico, and more - and often stayed.
Onwards and westwards, I headed to Porthgwarra. Set down twisting lanes, this hamlet is so romantically remote you feel you've time-travelled back to Poldark's late-18th century. It was here that the pilchard-fishing scene was filmed, and it was here that I stayed, my whitewashed cottage so perfectly positioned that it would surely win any contest for prettiest accommodation in Cornwall. Yet for all the fresh-air beauty, there's a strong mining connection. You reach the small beach via a slipway or along a tunnel running through granite rock. Created to give local farmers easy access to seaweed used for fertiliser, this was drilled in the 1890s by miners from nearby St Just.
The next day I explored St Just's bleakly bewitching landscape, studded with chimneys and crumbly looking mine buildings that in many cases are cliff-edge dramatic. The film crew had been here, too, shooting around the Botallack and Levant mines. It was Levant I especially wanted to see, for here there's a working steam-powered beam engine that hauled rock up from the shafts. I watched it in action - a fabulous arrangement of levers and hissing pistons - and I talked to the volunteer guides, learning how Levant's tunnels extended underwater 1600m from the cliff.
Up the coast I called in at Portreath, where I met Marion Symonds who runs Portreath Bakery and is passionate about the Cornish pasty. This poor man's food was the miners' staple work meal. Often unable to wash their hands, they would eat a pasty holding on to the crimp - the pastry seam on the side (never on the top for a proper pasty) which they would then discard. Arsenic was present in many mines, extracted for use in glass manufacturing and dyes.
Marion had recently returned from Mexico, where she explored the links between Cornwall and Hidalgo province. In 1826, a group of Cornish miners arrived there, revolutionising mining life - and they brought the pasty with them. Today, there's a pasty museum and even a pasty festival in Hidalgo.
North of Portreath is seal-enriched St Agnes, which stands in for Nampara Valley in the series. From here, I turned southwards to visit Charlestown on the outskirts of St Austell. Used for scenes of Truro, this is an untrumpeted gem; a beautifully conserved Georgian harbour, complete with a small collection of tall ships. It's a haven for film crews, too, and its screen appearances have ranged from The Onedin Line to the 2010 version of Alice in Wonderland. Its presence in Poldark is particularly apposite: Charlestown was constructed in the 1790s to service the mining industry. I strolled the old walls feeling out of sync in jeans and raincoat and then, with a sense of culture shock, drove back into the 21st century.
Getting there: Malaysia Airlines flies daily from Auckland to London, via Kuala Lumpur.
Accommodation: Corner Cottage, Porthgwarra, is owned and run by St Aubyn Estates Holidays. Sleeping two, it costs from $800 per week. The Rashleigh Arms in Charlestown offers two-night, B&B winter stays for a couple for $226.
Details: See poldarkmine.org.uk..
Further information: See VisitCornwall.com.