Nick and I are standing by the old Norman tower on the sacred isle. “We would come on the pilgrimage when we were kids,” he’s telling me. “Walk all around the island with thousands of others. All the cousins and friends doing the stations of the cross.”

We wander behind the tower, and in the trees are ribbons, cards and photographs. “It’s a bit pagan now,” he says, “but still very popular.” He’s a volunteer, helping to establish a new footpath, the Wexford-Pembrokeshire Pilgrim Way, which links south-east Ireland and Wales. I’m on my third day along the new footpath and have discovered that my route coincides with this more traditional Roman Catholic pilgrimage site at Our Lady’s Island near Rosslare, a venue that attracts around 50,000 pilgrims every August.

Pilgrimage in all its forms is back in fashion, having been out for several centuries, at least for much of Protestant Europe. In Britain, the obsession that had driven believers on the road to the holy city of Jerusalem, and its many substitutes, had been on the slide since King Edward I “Longshanks” landed back at Dover in 1274, the last Christian monarch to attempt recapture of the holy city (interfering in the Middle East is nothing new: his main achievement was to burn some huts near Nazareth).

Martin Luther subsequently dismissed any idea that visiting a sacred site could get you closer to heaven. Pilgrimage, he wrote, was merely “… the curiosity to see and hear strange and unknown things”. In other words, just travel.

But no matter, the desire to go to special places and line up with something cosmic survived, be it Glastonbury, Stonehenge or the pedestrian crossing on Abbey Road. And travel, particularly walking, remains an essential part. The Camino to Santiago de Compostela has become one of those bucket-list tickables, like doing Snowdon or Corsica’s GR20 or Everest base camp. No need for faith, except in the transformational possibilities of walking.

This new pilgrim route links Ireland and Wales, specifically the holy well of Maedoc in Ferns, south-east Ireland, with that of St Non, near the Pembrokeshire cathedral town of St Davids, a total of 162 miles, plus the three and a half hour ferry ride between Rosslare and Fishguard. Historically, this is the route supposedly taken by Irish shaman Saint Aidan (aka Maedoc), when he set off to study under the Welsh wizard Saint David. It’s a nice idea and happens to link up two highly attractive corners of the British Isles that, arguably, were once a lot closer than they are now. At the heart of the Irish section is Wexford, a lively fishing port with some fine pubs and cafes. (I recommend Harpur Eleven Coffee House for the memorable local speciality, the Wexford rissole.)

For those who want to take their pilgrimage seriously, there is a handsome booklet to be stamped at way stations, and the suggestion that you fill a bottle at Maedoc’s well and carry it with you. For those, like me, unversed in such matters it turns out that holy water is still a thing. I haven’t brought a suitably sacred vessel so make do with an old milk bottle.

I leave Our Lady’s Island and set off alone along the coast, heading for Carnsore Point, the south-eastern tip of Ireland where the Atlantic Ocean and Irish Sea meet. Around the coast here I’m getting the solitary pilgrim experience: not a soul in sight along the vast shingle beaches, just a washed-up whiskey bottle. Disappointingly there’s no message inside, or whiskey.

Although this section is off-road, a lot of the Irish route is on rural asphalt; the country does not have the network of footpaths found in the UK, a factor that creates difficulties when trying to establish a new route (and anyone who doubts that this advantage could soon be lost in England and Wales should read here). The Irish experience, however, has some major compensations. At Oulart Hill, I attend one of the regular music sessions at a thatched village hall, House of Stories: it’s a fabulous experience, rich in poetry and song. “We always have a real clatter of folk,” says John Dempsey, who runs the place with his wife Eileen, and himself delivers a fine line in hilarious verse.

Brian Ó Cléirigh, a local historian, tells me about “the ‘98”, the 18th-century rebellion against British rule that still resonates strongly in these parts, having led to the short-lived Wexford republic, before its inevitable and brutal suppression. Andrew and John Kelly sing powerful ballads and their dad, Joe, tells me about beekeeping and its relevance to the pilgrim path. “The legend is that Saint Aidan brought bees with him when he came back from St Davids. The honey was vital in those days.” The medieval Brehon laws of Ireland meticulously regulated beekeeping down to the compensation due if stung by a neighbour’s bee. To celebrate the path’s links with bees, each end of the pilgrimage will soon have three giant wooden hives that will amplify the sound of the colonies within.

With great sadness I leave Ireland and take the ferry to Pembrokeshire, ready for part two of the pilgrimage. The Welsh path mostly follows the coastal route, with some significant tweaks to visit holy places. Accompanied by path officer David Pepper, I get up the cliff from Fishguard, passing several neolithic sites and an ancient cross before we reach the holy well at Llanwnda. At the nearby chapel, David hands me a little pebble of white quartz to carry. “This was where the Breton saint, Gwyndaf, reputedly retreated after Saint Aidan gave him a beating,” David tells me.

I’m realising that if Saint David was your dove-like beneficent chap, his protege, Aidan, was more mettlesome. He’d give you a blessing, and a black eye. It’s not only the two saints that have opposing natures; the two sections of the path are quite different. If Pembrokeshire cannot quite match the convivial craic of Ireland, it delivers on landscape with vast clifftop panoramas punctuated by deep dips to isolated coves. Leaving David, I walk around Strumble Head, then stop my first night at Penrhiw, an organic farm that boasts not only a neolithic tomb on its doorstep, but homemade cheese. From there I push on and lodge at the excellent Ship Inn at Trefin.

Next day, at Whitesands Bay, I stand on the site of a ruined sixth-century chapel. Behind me is the hill where St Patrick reputedly heard his “call” to go back to Ireland. The waves here sometimes tease a skeleton out of the earthy cliff, the bones of people who may have known the saint. Children have appeared too: curled up in stone cysts with a quartz pebble on top. The distant past feels close in this landscape.

The end of the path, officially, is St Non’s well on the cliff outside St Davids. Non was Saint David’s mother who was raped and then abandoned to give birth alone, so the legend goes, on the cliff in a storm. I crouch down and add a little of the spring water to my Maedoc sample, unsure what to do. Drink? The simple act, however, does send an inexplicable deep resonance through me, like a huge bell heard through layers of stone.

Up the lane, at St Davids Cathedral, I meet Janet, who greets pilgrims who come to the place where Saint David’s bones are supposed to lie, and puts the last stamp in their booklets. She tells me that the 12th-century cathedral was built on a riverbed and one end is now more than four metres higher than the other. It’s the perfect place to finish: ancient and mysteriously wonky. At the shrine of Saint David, Janet reads from Irish poet, John O’Donohue.

When you travel, you find yourself
Alone in a different way,
More attentive now
To the self you bring along.

Further information: wexfordpembrokeshirepilgrimway.org. Guided Pilgrimage can organise guided walks along the Welsh section. Oulart Hill House of Stories has regular sessions at 8pm on the second Monday of every month