Sometimes you have to travel far to understand what you’ve left behind. Fifteen years ago, on a granite slab in the Rockies, a local climbing guide turned to me and said, “Ever heard of a place called Anglesey?”

We’d ascended to a pinnacle under an azure sky. The soaring rock giants of the American west stood sentinel all around. I was a beginner in rock climbing, but this looked about as good as it could get. He sighed. “Anglesey. I’ll go before I die.” He looked away with a thousand-yard stare, and added, gnomically, “A Dream of White Horses.”

Humans love naming the things they find. The first Europeans into America lavished their imagination on the landscape, hence Eureka Springs, Ginger Blue and Humptulips – a Terry Pratchett favourite. In Wales, religious mystics wove biblical legend into the hills: there’s Nasareth, Bethlehem and Paradwys. Rock-climbing routes are named by their discoverers, usually with similarly imaginative grandiloquence. A select few climbs become classics. An even smaller number become global superstars, sufficiently famous for a man from Wyoming, who had never been to Europe, to yearn to experience A Dream of White Horses, a route on the north stack of Gogarth.

He leaned back against the rock. “Solid-gold classic, man.”

Now I’m heading to Anglesey (Ynys Môn in Welsh) with climbing guide Henry Castle from Climb Pembroke, one of the country’s top sea-cliff climbing specialists. In the car, we discuss why routes become famous. “The moves, the rock,” he says, “and the journey.” He thinks a bit. “And the commitment. A Dream of White Horses is about commitment. Once you start, there’s no going back.”

I hope I can cope. I have two days to dwell on the fear while I do other things.

The kayak

Cemlyn Bay, on the north of Anglesey, is a lovely spot cut across by a shingle bank that has isolated a lagoon. If you can ignore the distant silhouette of the decommissioned Wylfa nuclear power station, it’s perfect. A footpath across the shingle makes a great platform for watching the birds that nest on the lagoon’s islands. Mostly it is terns – flocks of Arctic and sandwich – but there’s a pair of avocets, too, and oystercatchers. I explore the banks a bit and spot large mullet basking.

I paddle out, skirting the western side of the bay and rounding an island. Seals pop their heads up. Sea kayaking requires careful study of wind, tides and weather forecasts, but I’m heading out in slack water with a light breeze predicted to drop away under a clear sky. If you’re unsure, get a guide or do a course. Anglesey is renowned for its sea kayaking and there are several outfits. I’ve brought my own kayak, but they are available to hire.

When I get to the centre of Cemlyn Bay, I chuck out my spinner and haul it in. Ever since boyhood expeditions to fish the River Trent, I’ve known that I enjoy angling even when I don’t catch anything. It’s something about the focus, the way time stops. It happens so easily. The steady rhythm of the spinner: cast out, let it sink, haul in, repeat. When I’ve had enough, I find I’ve drifted east almost to the massive forbidding shape of Wylfa. I paddle back happy, like the fish I didn’t catch.

The hike

At Caerau campsite, the owner, Bente, tells me about the house where she and her family live. “It was founded by descendants of 14th-century Welsh nobleman Sir Gruffydd Llwyd [Rhys ap Gruffudd], but one of them married a gambler who lost the fortune and it fell into ruin. We’ve restored half of it.”

Bente also tells me about the hill that I’d noticed behind the house, marked on the OS map as Mynydd y Garn. “We call it Bonesetters Hill. The story is that a galleon was wrecked here and two boys survived. Neither spoke any language that anyone could understand, so it was assumed they were Spanish. The doctor who lived up there took them in.”

The younger boy proved to be an expert at healing broken bones and his grandson, Hugh Owen Thomas, became the father of modern orthopaedics. The story took a new turn in 2012 when DNA analysis of his descendants suggested they were from the Caucasus mountains, not Spain.

Whatever the origins, the hour-long walk up the hill is a lovely stroll to one of the great panoramas of Wales: in a vast sweep I can see the peaks of the Lake District, the Isle of Man, Ulster’s mountains of Mourne, then Ireland’s Wicklow mountains followed by those of Snowdonia. Bronze-age humans raised megaliths and stone circles, and this vantage point reveals what they knew: that the centre of the Earth was the Irish Sea.

The climb

The view also reveals Holy Island, the rocky outcrop connected to Anglesey by a causeway. Most visitors pile straight through on to the Irish ferries, but this ancient island is worth exploring. Beyond the town is Breakwater country park, the start for fine walks up Holyhead Mountain (Mynydd Twr), where the Romans built a lookout station. There is a huge amount of top-quality climbing on Anglesey, and a wide range of routes for beginners to the highly advanced. If you have never done outdoor climbing, get a guide and try it here.

My destination with Henry is Gogarth cliff on the far side – not a route for beginners. From here we abseil 50 metres to a ledge above the waves. Henry and I stare at the white face of rock that stretches to our left, ending in a huge sea arch surrounded by bottle-glass green water. How did Edwin Drummond and Dave Pearce, the discoverers of this journey in the 1960s, ever dare such madness? A Dream of White Horses is a daunting prospect, one that can overawe even the experienced climber.

We climb up and then left. Henry leads, placing protective safety gear in cracks. I follow, removing the gear, but always protected by the next fixed point. A fall will not be fatal. At last we reach the climax, a nerve-racking step around a fang of rock over the vast space of the “zawn” (or narrow sea inlet). A pair of kayakers negotiating the monumental archway on the promontory seem far below. (Agile walkers can, with care, reach the promontory and watch the climbing.) Henry goes first and I wait. The sun goes in and the swell picks up, crashing under me. Eventually the shout comes. My turn. I inch towards the fang, step down, reach around, connect with a handhold. My other hand slips. I fall.

I dangle, unhurt, protected by Henry’s carefully placed safety devices. He shouts: “Are you hurt?” I answer: “Only my pride.” I get back on the rock and finish the route, consoling myself with the thought that no one, apart from Henry, saw my fall.

Accommodation was provided by Caerau Campsite, with pitches from £19 a night. Guiding was provided by Climb Pembroke, which caters for all levels of ability; one-day courses from £260 for two people. Wild Wales by Daniel Start (£16.99) is an excellent guidebook for Anglesey adventures