DYRHAM 577 may not have quite the same resonance as Hastings 1066, but this obscure battle – the site of which now lies just south of the M4 near Junction 18 for Bath – was another crucial turning point in the history of Britain.

After the Romans left the island they called Brittania, the Celtic nations of Cymru and Kernow were referred to as ‘North Wales’ and ‘West Wales’ by their Saxon foe. But Dyrham began a separation process as Common Brittonic, the language once spoken across Great Britain and Brittany, branched into Welsh, Cornish and Breton.

In the 1,500 years since, Wales and Cornwall have continued to share remarkable parallels: long and remarkable struggles to keep languages alive, strong communitarian cultures based on religious nonconformity, working class love of rugby – and moments of revolt.

The Glyndwr Rising of the early 1400s has counterparts in the Cornish Rebellions of 1497 and the Prayer Book Rebellion of 1549.

In recent decades, both have experienced the decline of traditional industries, most notably mining – china clay and tin in Cornwall; slate and coal in Wales.

And in both places the socio-economic devastation that followed has been accompanied by gradual, steady increase in discussion around self-determination, with a growing movement for independence in Wales, and increased calls for further devolution to Cornwall.

All Under One Banner (AUOB) is a grassroots campaign movement that organises family friendly marches in the Celtic nations, and just as in Wales, marches are planned for the autumn in Cornwall.

The next, planned for October 9 in St Austell, will bring together Cornish independence campaigners with others who want at least a degree of devolution.

And just as Welsh nationalists sometimes look to Scotland with the idea of its being further ahead in what is understood to be a journey toward independence, supporters of Cornish autonomy often look to Wales.

In fact, writer Tim Hannigan says Wales is the only place where there’s broad recognition that Cornwall is not England. But he does not attribute this to a deep-rooted historical connection.

“It’s absolutely true that culturally and linguistically Wales and Cornwall and Brittany were part of one bloc and Ireland and Scotland another,” he says.

“But I think it’s a more recent thing – and is to do with a greater proximity to England and Englishness."

Falmouth Packet: Tim Hannigan. Picture: Cara GlynnTim Hannigan. Picture: Cara Glynn

He added: “Ireland is an independent country. They don’t need to worry about England any more, although you could still argue that Irish identity is partly constructed against Englishness.

“Scotland is robustly, distinctly quasi-independent, possibly on the way to being fully independent. In terms of identity and status, they are less troubled by England.”

By contrast, he feels the ambiguity Wales and Cornwall share creates solidarity between them. “As strong as Welsh identity is, politically it’s less satisfactorily separate – and Cornwall isn’t separate at all.”

Although Hannigan was generally supportive of Scotland’s 2014 bid for independence, he worried about what it might mean for the rest of the UK, particularly his native Cornwall.

National minority status was conferred on it that same year by David Cameron’s government, and Hannigan says: “Lots of people were like, ‘we were only joking – what do we do now?’. I like the slight ambiguity that Cornwall has. If Scotland went, there would have to be a hardening of that place Cornwall exists in. The humour would be taken out of it.”

Hannigan admits there has often been a ‘tongue-in-cheek’ dimension to Cornish national feeling, played out in humour, self-deprecation and a tradition of dialect stories – “pretty excruciating, actually, because they don’t really sound Cornish” – that developed in the 19th century as the language declined, and the way this performative, exaggerated Cornishness has more recently been expressed through stand-up comedy by acts like Jethro.

He says: “It’s easier for Wales because Wales is unambiguous. It’s not England, it’s a separate country. Whereas Cornwall – and I’ll get in trouble for saying this amongst the more strident Cornish nationalists – is ambiguous.

“Administratively it’s a county, yet it has this identity and heritage which is not that of a county. I’d be sort of sad if that blurriness, that uniqueness, was lost.”

Garry Tregidga, director of the Institute of Cornish Studies at Exeter University, explains that many people in Cornwall “feel that they are different – Cornish, maybe British, but certainly not English – but don’t know what to do about it” – and attributes this to “long-term economic paralysis”.

“From the 19th century, the Cornish economy effectively collapsed, and we have been forced into the English economic sphere through mass tourism.”

But locals feel powerless. “People feel there are too many holidaymakers – but what do we do about it?”

Falmouth Packet: Garry TredgidgaGarry Tredgidga

He says that after Gwynfor Evans’ famous victory in the Carmarthen by-election of 1966, there was a sense Mebyon Kernow (MK) – Cornwall’s nascent Plaid Cymru equivalent, “which was then a pressure group rather than a political party” – were “joining in with what was happening in Wales and in Scotland”. Unlike in other Celtic nations, where nationalist parties have become fixtures of the political scene, he says: “Somehow or other we [in Cornwall] seemed to lose our way.”

One reason he posits for the difficulty Cornwall has faced developing a meaningful devolution movement is a lack of political leadership.

Tregidga still wonders whether David Penhaligon – Liberal MP for Truro from 1974-86, popular across parties before his tragic death in a car crash – would have made a natural political leader of Cornwall.

The Liberal Democrats have often been seen as a regionalist party in the south west of England, and Tregidga sees a ‘progressive alliance’ between the Lib Dems and MK as a potential way forward for Cornwall, but explains that since 2015, the Conservatives have had some success “trying to present a local image through gestures – such as wearing tartan ties”.

It might come as a surprise to learn that the electoral map of Cornwall is currently totally blue, with six Conservative MPs. Tregidga explains simply: “Brexit appealed to Cornish voters.”

“In mid Cornwall, where there is the highest MK vote, there was also the highest Brexit vote.”

Counterintuitive at first glance, it is an explanation that will make sense to anybody drawing comparisons between Cornwall’s former clay country around St Austell and former tin-mining towns like Camborne and Redruth with places like Merthyr Tydfil and Blaenau Gwent that also voted heavily to leave the European Union.

Like Wales, Cornwall faces many immediate socio-economic problems. Top of the list is housing.

As in Wales, pressures on local communities have been exacerbated by the popularity of so-called ‘staycations’ and the boom in short-term lets via sites like Airbnb.

Tim Hannigan knows lots of people who live in their parents’ gardens - “people in their forties who have done things of varying degrees of legality” in order to continue living in the communities in which they were born and raised.

Without mentioning names, he lists friends and acquaintances who have “a wholly off-radar house in a back garden”, “a house built inside a barn” and “five or six people I went to school with who live in sheds in their parents’ gardens, sometimes with their own families”.

Hannigan compares the rapid progression of Cornwall’s acute housing crisis to the slow decline of its language.

“If you look at maps of how Cornish retreated from the medieval period, the same thing is happening now with the availability of affordable housing; it’s just shrinking away.

“Ten years ago, young professionals could just about afford a house in Penwith or St Just.

“Then that got too expensive, so people started buying in Hayle. Now it’s Camborne and Redruth. After that there’s nowhere else to go. And this is teachers, nurses, doctors.

“How can a place function if primary school teachers are having to commute from Camborne and Redruth to Land’s End, or to the north coast? I don’t know what the endgame is.”

Garry Tregidga sees some hope in the fact MK is “starting to attract the support of progressive voters who have moved to Cornwall, people who are concerned about the morality of second homes”.

But just as in Wales, where we are used to seeing some of our local authorities perpetually at or near the bottom of UK-wide socio-economic league tables, Hannigan says Cornwall’s biggest problem is ‘general poverty’.

“This is where the semantically constrained Cornish nationalists have difficulty formulating their words,” he explains.

“Because Cornwall is the poorest county in England by lots of measures, but you must never call it a county.”

Pressed on the causes, it is again hard not to draw parallels with Wales.

“It’s a place that had industry that created urban centres – St Austell, Camborne and Redruth,” says Hannigan. “And then the industries were taken away.

“If you block a bunch of population together and then take away meaningful employment, you have entrenched social problems, don’t you?”

For the visitor to Cornwall’s picture postcard coastal villages – where a two-up two-down fisherman’s cottage can now fetch £1.5m – these problems can be difficult to discern.

“Cornwall looks nice,” says Hannigan. “It looks affluent. Even if you drive through the residential areas of Bodmin or Camborne or Redruth, you can see fields everywhere.”

It is a haunting vision.

For a week or two each summer, visitors to Cornwall enjoy art and ice-cream; surfing, sunbathing and seafood; windswept coastal walks. Beneath their feet an ancient culture is silently eroded like the cliffs.

And for Tregidga, and a growing number in Cornwall: “Culture is linked to politics. It’s not just a community, but a nation that’s being destroyed.”