It was a wild place to build a castle, but it was probably also largely symbolic, said Win Scutt, English Heritage’s senior properties curator, as he showed me around.

“It had no strategic significance for Richard Earl of Cornwall back in the 1230s. It had no garrison, and in all likelihood it was built just to capitalise on the drama and the romance of Arthur,” he explained. Apparently, the legend was huge even back then, thanks in part to cleric Geoffrey of Monmouth, who wrote The History of the Kings of Britain in 1136 and gave Arthur a starring role.

In the legend, Tintagel/Camelot was where Arthur was conceived, albeit in rather murky circumstances. His father, Uther Pendragon, was infatuated with Igraine, the wife of the Duke of Cornwall, who lived there. Uther enlisted the help of Merlin so that he could assume the Duke’s appearance and slip into the castle, and thus to milady’s bedchamber. Arthur was the result – although he was removed by Merlin while still a baby.

All this supposedly happened in the late 5th and early 6th centuries, a time when there were at least 100 houses on the promontory at Tintagel. Win showed me the older buildings and speculated that there could have been many more – “We do know it was a seat of power.”

Extensive pottery finds from this period have also thrown up connections to the eastern Mediterranean. “That suggests a major development,” explained Win, yet archaeologists have since found no physical evidence of the existence of a certain chivalric king with an overdeveloped sense of justice. But that doesn’t stop people wanting it to be true.

“Back in the 1960s, we were very po-faced and made no mention of Arthur,” Win continued. “But the castle was built on the myth, and that’s why everyone comes here, so we have stopped ignoring the legend. These days we acknowledge that this is a place where myth and history meet.”

Live by the sword…

With its magnificent coastal views and bags of romance, you can see how stories grew around the Tintagel promontory. The castle is best experienced on a wild and windy day, when the waves thunder into the rocks and seals shelter in the middle of the bay. But this isn’t the only part of Cornwall where you can live out your dreams of Arthurian legend.

King Arthur’s Great Halls were created in Tintagel village in the 1930s by Frederick Glasscock, a man who made his millions from powdered custard. His vision of an Arthurian meeting hall is stashed behind a normal suburban façade on the main street and decked out with thrones, banners, velvet drapes and elegant stained glass. A portentously voiced audio-visual guide in the inner hall gives an overview of Arthur’s life; this is also the place to sign up for the Fellowship of the Knights of the Round Table, if that’s what you’re into.

Arthurian legend infuses much of this region. Some 30km south, on the edge of Bodmin Moor and just beyond Jamaica Inn (a historic meeting place for smugglers that was made famous by Daphne du Maurier’s novel), lies Dozmary Pool, the home of Viviane, the ‘Lady of the Lake’. It was her arm that extended above the waters to catch the sword Excalibur after it was flung by Sir Bedivere, as Arthur lay dying. Dozmary today is still a lonely place, with one solitary house by the water’s edge. Sadly, not having a sword to fling, I wasn’t able to ascertain whether any underwater sorceresses were now in residence. I also had other traces of the legend to track down, far from here.

The other side of the story

After visiting Dozmary, getting to my next Arthurian location required hopping the Channel to France, yet the change of scene bought more parallels than differences.

The ancient forest of Brocéliande, south-west of Rennes in Brittany, is a patchwork of deciduous and coniferous trees fringing small villages. Like Cornwall, its people are Celtic and have their own language – now mostly died out. Also like Cornwall, there is a profusion of stone circles, ancient tombs and legends. But one story in particular stands out.

Brocéliande’s Tintagel equivalent is the village of Paimpont, an orderly place made up of rows of ironworkers’ cottages on the edge of a lake. There’s a former monastery, which is now the town hall; an abbey church; a sprinkling of shops that sell minerals, crystals, and dream catchers; a bar named Lancelot; and a shop and guesthouse known as the Grail House, which sells statuettes and mead.

Here, too, there was an audiovisual guide, La Porte des Secrets, provided by the tourist office. It’s done with flair, full of voices and lights and special effects, and it talks of pixies and elves and forest legends, with Arthur chief among them. But to find purer Arthurian content, you need to head for the 14th-century Château de Comper in nearby Concoret, whose Centre de l’Imaginaire Arthurien is a focal point for research on the legend and for developing the imagination of its visitors, both young and old.

“Back in the Middle Ages, the legend was a hit across Europe,” explained Arthurian expert Nicolas Mezzalira. “It was a time of travelling storytellers, so this legend escaped its origins. All the courts of Europe knew it… Back then, there was no TV.”

He showed me the château’s lake, reputed to be Lady Viviane’s second home, after Dozmary – or should it be the other way round? So the story goes, her boyfriend Merlin created for her a glittering palace, hiding it beneath the surface. Here she fostered a young child, Lancelot du Lac, who she schooled to become the world’s greatest fighter.

Do visitors really believe there’s an underwater palace, I asked? Mezzalira shrugged. “It depends on your imagination. Imagination, stories – these are just doors to enlarge our experience; to introduce us to a wider reality.”

One thing is for sure: the character of Lancelot is a distinctively French addition to the Arthurian lexicon, introduced by the medieval poet Chrétien de Troyes, who was also responsible for popularising the idea of the quest for the Holy Grail in the 12th century. Others contributed to the French legend, and its tales spread. English writer Thomas Malory’s 15th-century version of the story, Le Morte D’Arthur, was translated from French sources.

Today’s school students in Brittany even study Arthur via a novelisation written by Xavier de Langlais in the 1960s – or so I learned from Lindylou, a local schoolteacher and storyteller who was instantly recognisable from her trademark black-velvet hat. She met me at the entrance to Brocéliande’s Valley of No Return, where we walked and talked.

“The Valley was named by sorceress Morgan Le Fey, who was King Arthur’s half sister,” Lindylou claimed. The story goes that Morgan had had an assignation in the valley with a handsome knight, but when she came upon that place again, she found him kissing another woman. “She was so angry that she turned them to stone, declaring that from then on, anyone who was unfaithful in heart and mind that entered into the valley would never be able to leave.”

Once we’d examined the gorse-covered saddle of purple rock where the lovers had been petrified, and admired the Golden Tree (the skeleton of an oak that had been covered in gold leaf by an artist to mark a forest fire), the valley let us go. I asked Lindylou if that meant we were pure in heart and mind. Her answer was decidedly non-committal: “We were undetained.”

She later took me to see a curious little church in Tréhorenteuc, a pretty village nearby where legend and religion have become intertwined. In the mid-20th century an eccentric priest named Abbé Gillard was so immersed in the stories of Arthur that he placed the Holy Grail centre stage in the village church’s stained-glass windows, and commissioned Round Table paintings for its walls. The Abbé was a popular man in the community, but disapproving church authorities eventually moved him on.

Before we parted, Lindylou suggested other Arthurian locations that I might visit. This region has become a kind of French mecca for alternative lifestyles, fuelled by the myths and legends that lurk on street corners. Even the walls of a local primary school were adorned with the head of an enormous blue bull, whose horns devolved into serpent-like tendrils. The stuff of nightmares for little boys and girls.

I visited the ancient Forges de Paimpont ironworks, where many Cornishmen – another Celtic connection – had once come over to work. I went to see what was supposed to be Merlin’s tomb, although the collection of stones that I found could have been anyone’s burial place – especially in a part of the country that is littered with standing stones. And I stopped at the newly created round table in its glade of trees, set inexplicably in the heart of the village of Néant-sur-Yvel, where a metal Arthur glowers across the table at Sirs Gawain and Kay. It’s a new artwork, sponsored by Les Nouveaux Chevaliers de Brocéliande, and I was told the whole table will eventually be populated with more knights.

Finally, I took myself out to Barenton, Merlin’s spring. Here, legend has it that those who transgress by sprinkling water on its sacred rock will summon a Black Knight and stir up a thunderstorm. The spring turned out to be set in a rather charming glade, reached via a path covered in a pine needles. At its centre, a pool of completely clear water bubbled with the periodic release of nitrogen from underground, but otherwise the wood was still.

I sprinkled some water on the forbidden rock to test the legend. No Black Knight appeared, although it did rain, shortly thereafter. Brittany, as with Cornwall, doesn’t get to be this green without the heavens opening occasionally.

It was there that my deep dive into the kingdoms of Arthur, on both sides of the Channel, ended; not with a storm of revelation but, more fittingly, the slow drip of legend all around. I had found Tintagel and Brocéliande to be compelling places in their own right, and you can see how the stories grew around them. As to whether Arthur actually existed, I can only refer back to the words of Nicolas Mezzalira: “A storyteller is just a liar telling us a truth.”

The author travelled with support from Brittany Tourism and Brittany Ferries.