A divine sunset requires a divine prelude. Armed with a flask of gin and tonic, in air perfumed with honey and herbs, I follow a sandy track bisecting two mighty volcanic cones, cross a sloping lava plain and flop on Las Conchas beach’s honey-blonde sand.

Behind me looms a third volcano, this one a rich rusty red. In front: rolling barrels of surf, the Prussian blue Atlantic and a deserted island’s sculptural rocks. Nuzzling the horizon, a burning sun rages against the dying of the light. Next stop, the Bahamas.

I clink my iced sundowner and contemplate the neighbourhood. It’s not just beautiful – serenely, starkly, heartbreakingly beautiful – it’s empty. I haven’t seen a soul since my guesthouse. The coloured mountains, powder sand, widescreen ocean; I have them to myself. Glorious isolation indeed.

The solitude is perhaps unsurprising. La Graciosa, an otherworldly speck of volcanic creativity off northern Lanzarote – officially recognised as the eighth Canary Island in 2018 – remains buried in lava, far below mainstream tourism’s radar.

La Graciosa’s vital statistics speak for themselves: six beaches, four volcanoes, no sealed roads and, apart from occasional 4WD taxis, no cars. Its one town, Caleta del Sebo, hosts a few guesthouses, rental apartments and cafés, alongside a supermarket, church, “discoteca” and 730 chilled islanders.

It’s alien to anywhere I’ve seen in Europe. Harsh but beautiful. Yet the 17 square miles of La Graciosa provides a quandary. While the locals’ sun-kissed languor is infectious, the potent blend of small-scale island and epic scenery induces immediate lethargy guilt. I kick back for a day, yawn, stretch, then give in. 

Peeling myself off a beach towel, I hike around the southwest corner’s precarious coastal path to La Cocina Beach. First sight is unforgettable. Emerald seas lap white silica grains beneath Montaña Amarilla’s mottled yellow face, its sulphurous lava long solidified into a giant Crunchie bar. When another sunbather arrives an hour later, I depart in a claustrophobic huff.

Another day, another photogenic beach. La Francesca: a symmetrical curl of powdery sand with water of Maldivian translucence. In late afternoon’s purple haze, I lie in its warm shallows counting Lanzarote’s serrated blade of volcanic peaks across the Atlantic. I stop at 17: scenic grandeur to rival Chile’s Atacama Desert.

La Graciosa’s discrete charms are no secret to Canary Islanders, of course. Hiring a mountain bike – it’s impossible not to whoop with glee as you zip beneath the hulking cone of Agujas Grandes – I visit Pedro Barba’s petite cluster of chic-rustique holiday cottages whose gardens of palm, cactus and bougainvillea overlook Lanzarote’s immense Famara cliffs. Selling for over a million euros a pop, the properties are rumoured to be owned by Canarias politicians and A-listers.

Caleta del Sebo’s sandy spaghetti-western streets are a little less rarefied. Fish first attracted settlers to the island in the 19^th century and remains central to the town’s culture. Its tiny church of Nuestra Señora del Carmen contains a supersized specimen hewn from volcanic rock, a font forged from a turtle shell lashed to a lobster pot, and walls draped in nets. A figurehead of Mary, recycled from a ship’s prow, overlooks an altar balanced on an anchor, its candles flickering on carved wood fish: a minimalist’s theological nightmare.

In summer, hundreds of salted vieja fish, their mouths resembling parrots’ beaks, are hung out to dry like boxer shorts on a washing line. After several decent catch-of-the-day suppers, I brave La Graciosa’s signature Caldo de Pescado (seafood stew) at waterfront Meson de la Tierra. Preparation takes two days. It must be special. Anticipation builds. Forty-eight hours later, my palate prepares to be tickled.

The dish is certainly special. It appears to originate from a decaying coffin rather than a kitchen. Savage bones, clammy flesh and fish slabs bob in a glutinous mire. I close my eyes, offer silent prayers and dig in. It tastes better than it looks. Just. I later tell the waitress it was wonderful. I’m British, it’s what we do. Never again.

It’s perhaps time for a change of scenery. That’s tricky. Around here, a change of volcano is your sole option. La Graciosa is the only inhabited island in the Chinijo Archipelago Natural Park’s sprinkle of lava-coated peaks and cones. Exploring it involves joining an eco-cruise, bumping across wind-whipped seas alongside turtles and flying fish – evidence we’re in Europe’s largest marine reserve with 300 different types of seaweed and many protected bird species, from osprey and Eleonora’s falcon to white-faced storm petrels.

We anchor directly beneath Alegranza’s 900ft-high cliffs: the west face of the island’s main caldera. After swimming above underwater tiers of magma resembling vast lily pads, we snorkel past purple and gold-flecked rocks into a cave with coal-black sand and jade-hued water.

It’s equally colourful, but more spectacular, in the 50 square miles of Lanzarote’s Timanfaya National Park. A backdrop to Pedro Almodóvar’s Broken Embraces, the landscape is more Hades than lunar, with avenues of orange, copper and burnt ochre volcanoes spiking through a dark, menacing lava plain.

In parts, the thin scarlet and cream crust mingles with grey ash. Beatrice, our guide, pours water into a 20ft-deep hole where 400C heat produces an explosive geyser of steam. Timanfaya is, as Nobel prize-winning author José Saramago observed, ‘either the beginning or the end of the world.’

Hours later, I stop at northern Lanzarote’s Mirador del Río, one of artist César Manrique’s naturalistic landmarks. Time for a final elegy-inducing sunset. From 1,558ft I gaze down onto La Graciosa’s mountains and beaches washed with soft buttery rays and recall an earlier conversation with the island’s former mayoress. ‘In September the wind softens to a gentle caress,’ said Margarita Páez Guadalupe. ‘The light’s golden and this place becomes the authentic El Dorado.’ She knows of what she speaks. I’m coming back.

Eight-person Casa Lajares in Pedro Barba from £147 a night, airbnb.co.uk. Lanzarote flights from £117 return, britishairways.com. Return ferry to La Graciosa, €28, biosferaexpress.com