DAN JONES: For me a great British castle is a fortress, a palace, a home.

And a symbol of power, majesty, and fear.

For nearly a thousand years, castles have shaped Britain's famous landscape.

These magnificent buildings have been home to some of the greatest heroes and villains in our national history.

And many of them still stand proudly today, bursting with incredible stories of warfare, treachery, intrigue, and even murder.

Join me, Dan Jones, as I uncover the secrets behind six great British castles.

This time, I'm exploring one of the most stunning castles in the land.

This fortress was built on tyranny and has survived the bloodiest rebellion.

It's a great Welsh castle, where love and sex, birth and death, all come together.

And beneath it all is a power struggle that helped create Britain as we know it today.

Today, Caernarfon is a quaint little seaside town where busloads of tourists come for day trips.

And the reason it has so many visitors is its castle.

Caernarfon doesn't just look like the perfect medieval castle, it's a place that's right at the heart of the story of Britain.

A story of myth, legend, rebellion, conquest, and the struggle for the right to call yourself Prince of Wales.

NEWSCASTER: The gray fortress was a place of rejoicing on this day.

While the crowds cheered their monarch, the young prince, with a dignity and assurance belying his years... JONES: In the summer of 1969, Charles Windsor, the Queen's eldest son, was created Prince of Wales.

The ceremony was rich in significance, and so was the place it was held.

NEWSCASTER: A modern prince in a medieval castle kneeling before the Queen.

To live and die against all manner of folks.

JONES: It's no accident that the heir to the throne of England has been called the Prince of Wales.

And Caernarfon Castle is at the center of that story.

Today, the title Prince of Wales is largely symbolic, but in the past, its power has been very real.

The Prince has been someone to save Wales, to protect Wales, and to control Wales.

And all that real and symbolic power comes together here at Caernarfon Castle.

The Queen knew it when she invested Prince Charles on this spot.

And the man who built this castle, King Edward I, well, he certainly knew it.

This is a brute of a fortress.

Caernarfon Castle is unashamedly intimidating.

And so was the man who built it at the end of the 13th century.

Wherever Edward I went, he left his mark on the landscape in stone.

Here at Caernarfon, he created one of Britain's most impressive castles to show off English dominance over Wales.

But before any of that could happen, he had to crush the Welsh.

In 1274, Edward I returned from the Crusades to be officially crowned King of England.

(SPEAKING FOREIGN LANGUAGE) Amen.

JONES: But for Edward, an ambitious warrior king, ruling England would never be enough.

(SPEAKING FOREIGN LANGUAGE) Amen.

JONES: The new king had set his sights on something that for 200 years no English ruler had ever managed to do.

He wanted to conquer Wales.

And Caernarfon Castle would be at the center of this conquest.

It was said that the Welsh were very easy to beat in a single battle, but very difficult to beat in a war.

The Welsh were masters of what we'd now call guerilla warfare.

They used the terrain and the weather to their advantage, and they specialized in ambush and night attacks.

To the outside world and particularly the English, they were noble savages with long hair and bare legs against whom the normal rules of war didn't apply.

Here, in the forests of Snowdonia, just a few miles from Caernarfon, the powerful native Prince of Wales, Llywelyn ap Gruffudd had waged sporadic war against the English for many years.

In 1276, Edward set out to destroy him.

By the summer of 1277, Edward had raised a massive army of 15,500 men, 10 times as many as he had taken on Crusade.

Edward's invasions of Wales were real shock-and-awe affairs, literally cut a swathe straight through the forests of north Wales.

As he went, he seized castles, took at least seven from the native Welsh princes.

But better than that, he also had a plan.

A radical new weapon for the total conquest of Wales.

That new weapon was stone.

Edward needed to secure his victory and power over the Welsh.

He commanded his engineers to create a ring of castles around north Wales reaching from Aberystwyth to Conwy.

In each castle he could leave a permanent garrison of soldiers.

At the first sniff of Welsh rebellion they could ride out and crush it.

Edward's troops tore through the countryside leaving their marks of conquest on the landscape like the blows of a great stone hammer.

And nowhere did that hammer fall harder or sink deeper than here at Caernarfon.

Stuart, here we are on the edge of Snowdonia, next to the water.

Why is Caernarfon Castle here?

It's part of a chain of castles, the Ring of Iron.

Okay, so, the last bastion of Welsh resistance to the English was essentially centered in north Wales around Snowdonia.

It was the rebel base, if you like.

And so Edward needed to find a way to suppress that, kind of, continual rebellion.

So what he did was he constructed a chain of fortresses around Snowdonia, a whole series of them.

This is one of those castles.

So, essentially you've got a continual reminder, if you like, that your land has been taken and it can be held against you.

So this castle is all about Edward I stamping English power in a ring right round Snowdonia, right in the heart of rebellious Wales?

You've got it in one, and if you build in stone, you're there to stay.

JONES: Edward was determined that Caernarfon would be a fortress like nothing the Welsh had ever seen before.

Work on the castle started in 1283.

To oversee construction, Edward hired one of Europe's greatest military architects, Master James of St.

George from Savoy in eastern France.

Over the next 12 years, Master James would design six of Edward's castles.

Caernarfon shows us the very best of his skill and experience.

Now, Master James didn't build Caernarfon Castle all on his own.

He was a sort of master foreman who specialized in putting up castles in double-quick time, four to eight years in most cases.

And of course, that took a lot of manpower.

In 1285, there were 1,000 men working on Caernarfon Castle alone.

He used cutting-edge technology to create a siege-proof castle, and nowhere was that more evident than at Caernarfon's main entrance.

The King's Gate was the most fearsome threshold of any British castle.

So, Stuart, this is the nice tourist entrance way to the castle at the moment, but actually, this would have been one of the most dangerous bits of the castle to be in, wouldn't it?

Basically, this was a gateway like none other.

It's complete overkill.

This thing ran all the way past you and right round the corner.

So it was a big, kind of, you know, angled structure, right- angled structure, and within that structure, five gates.

JONES: One after the other, just in sequence like that?

Up above you've got the classic murder holes where the hot sand is being poured through, goes in all the chinks in the armor, burns you alive.

And then, either side of you, you've actually got arrow slits.

It is a statement, as well, about power, obviously, but, I mean, it does make this gateway absolutely indestructible.

JONES: The Welsh trembled in the shadow of Caernarfon Castle, and its warlord, Edward I. But what they didn't know, was that one woman had a huge influence over the King, the castle and the future of Wales.

She was Edward's queen, Eleanor of Castile.

The conquest of Wales was driven by one of the greatest love stories of the Middle Ages.

To secure his conquest of Wales, the great English warrior king Edward I, built a massive ring of stone castles to scare the natives into total submission.

Caernarfon was the bedrock of this conquest.

If you want to subjugate an entire land and its people, this is how you do it.

Caernarfon wasn't just supposed to be a great fortress.

It was also intended to be a magnificent royal palace.

He needed a palace, because when he wasn't fighting, Edward was building a large royal family.

He did it with the support of his beloved wife, Eleanor.

She was a powerful and intriguing woman from Northern Spain.

Edward loved his queen deeply, which for arranged royal marriages was pretty rare.

To bring Wales under the rule of the English Crown, Edward and Eleanor came up with a brilliant political plan.

And how much of a political influence do you think Eleanor was on Edward?

I think she was a huge political influence because she came from a family which thought very deeply about what the role of a king should be, and also what the role of a conquering king should be in pacifying a conquered nation.

And so she had all the theory behind her, which the English kings frankly lacked in the recent years in terms of conquest.

And so she was very much able to advise him in terms of military approaches and administration.

There has been this idea that she was the, kind of, perfect medieval, submissive queen.

Whereas the real woman was very dynamic, very intellectual, um, very hard in some ways.

A very successful businesswoman who built up a massive property empire, which kept the queens of England solvent for centuries.

JONES: Sara, history remembers Master James of St.

George for physically building the castles and Edward for having the political vision, but are we overlooking Eleanor's role?

Well, I think when you look at the design elements of the castle, I see an influence from her in the very shape of the Eagle Tower, which does have a resonance of the Castilian seal, which was a polygonal tower with three turrets just like the Eagle Tower.

JONES: So the Eagle Tower which we see here with its three turrets and its polygonal shape is a symbol of Castile?

A polygonal tower with three turrets was the symbol of Castile.

JONES: For the ambitious King Edward, military rule alone wasn't enough.

To make his power permanent, he had to seal his conquest in blood.

Edward had his defensive ring of castles with Caernarfon as the jewel in the Crown.

Now, could Eleanor give him the one thing he needed to solidify political power?

A prince.

By the time construction on the castle had started in 1283, Eleanor and Edward had had 15 children.

Their eldest son Alphonso, was heir to the throne, but many of the others had died young.

For insurance, Edward was desperate for another male child.

So Eleanor, like all aristocratic mothers-to-be, turned to the latest, and weirdest, medical advice to help her conceive another boy.

After all, the future of the dynasty depended on it.

So, Lydia, how did people think about conception in the Middle Ages?

They did come up with different remedies.

Um, so for example, if a woman wanted to not conceive, they would say to take body parts of animals and to put them around her neck and wear those during sexual intercourse, to stop her from having a conception.

So literally a necklace with different parts of... Literally around her neck, yeah.

JONES: And as we know, politically, in the Middle Ages, it was better to have a son than a daughter, alas.

How did people in medieval times try and make sure they conceived a son instead of a daughter?

HARRIS: Well, there's lots of little things that they tend to go about doing during the act of sexual intercourse.

So for example, if a woman clenches her fist during intercourse, that's said to conceive a male.

Um, if the male has strong virulent thoughts during sexual intercourse, then he should be then able to conceive a male.

If he looks towards the direction of the sun, then hopefully he will be able to conceive a male child as well.

So there's different combinations of almost a folkloric, and a medical tradition that tend to find their way into medieval medical manuals.

So presumably, if you put them all together, -clench your fists, look at the sun... -(LAUGHS) And what was the other one?

I can't remember.

Then your chances are gonna be tripled.

Um, one would hope, but I'm pretty sure it didn't actually have that much of an effect.

Very much a placebo effect, possibly.

JONES: Edward and Eleanor arrived here in Caernarfon in July 1283, just after building work started on the castle.

And straightaway, Eleanor conceived her next child.

So you have to ask, was that an act of passion brought on by the romantic Welsh countryside?

Well, far more likely it was an act of hard-nosed politics.

But this would only pay off if she had a son.

Nine months later, Edward asked the heavily pregnant Eleanor to make a long journey from the east of England to northwest Wales.

Edward's queen was to give birth to a prince, and she was going to do it in Caernarfon Castle.

Was it more dangerous, in some ways, to give birth as a queen than as, say, a farmer's wife?

Um, I would say yes, mostly because there was a lot more pressure as well that came with the birth.

So, that obviously would put a lot more stress on the woman herself.

If you combine that with someone like Eleanor, who's constantly on the road, she's constantly being jostled around, the roads are not smooth, they're very bumpy.

And if you're quite pregnant at this time, already dealing with the stress of having lost so many children and lost so many heirs and wanting to produce a son, that would have caused a much more dangerous situation for her.

By all accounts, the medieval birthing chamber would have been a very terrible place.

They would have closed the windows, um, shut the woman in.

They thought the air coming in would have been bad for the child.

So, it would have been a very hot, miserable, damp place to have to deliver a baby.

(ELEANOR SCREAMING) And obviously, but if you're a woman like Eleanor of Castile, it's a little more difficult if you're in the middle of so much political disarray, obviously, with Edward's wars going on and, um, having to be in an unfinished building, and everything else.

It wouldn't have been the most comfortable place to be.

So it's quite unusual, um, for a queen to ever really have a nice calm, safe pregnancy.

They always seem to be jostled about or on the road somehow.

Poor Eleanor, and she went through this, what, 16-18 times.

Mmm-hmm.

Over the course of the better part of two decades.

Yes.

JONES: On the 25th of April, 1284, Eleanor gave birth to her 16th child.

Since the castle was still under construction, the child was probably born in a temporary outbuilding.

But all the danger and discomfort was worth it.

Eleanor had a son.

They named him Edward after his father.

An English prince born in Wales.

Edward had huge political intelligence.

He was a master of what we'd now call propaganda or PR.

Edward was determined to win over the Welsh, and legend has it, one of the tricks he pulled was to promise he'd name one of their own as Prince of Wales, only to present them with his own infant son, saying he gave them a prince born in Wales, who did not speak a word of English.

The new prince arrived in the nick of time.

Just four months after Edward was born, his older brother Alphonso died.

The new baby was heir to the throne.

And from now on, "Prince of Wales" would be an English title forever linked to Caernarfon Castle.

But let's not forget about the child's mother.

Eleanor was 42 when Prince Edward was born.

She'd bear 16 kids at least, for the king, that's one every 18 months.

Between the perils of childbirth, her loyalty to her husband and a desire to travel, she'd eventually work herself to death at the age of 49.

Eleanor died from fever in 1290.

Her death brought one chapter of Caernarfon's history to a close, and it left Edward almost inconsolable.

To honor her memory, Edward ordered the building of 12 great memorial crosses along the route of her funeral procession, all the way from Lincoln to London.

The last of these was at the village of Charing, now called Charing Cross.

In December 1290, Eleanor was interred here at Westminster Abbey.

Her tomb lies near her husband Edward's.

Now close in death, as they were in life.

Queen Eleanor had died helping bring Wales under English control.

But the conquest of its resilient and defiant people was far from complete.

Edward had land, he had his castle, he had a prince, but he still didn't have complete political control because outside these walls there was still serious unrest.

And Caernarfon would be at the center of a new Welsh rebellion.

Caernarfon Castle was a powerful symbol of Edward I's conquest of Wales.

It was also the birthplace of his son, the next in line to the English throne.

But the Welsh weren't about to take this lying down.

Rebellion was coming.

Edward and his army of builders didn't just put up this magnificent castle, they also created a bustling town protected by steep town walls, which they filled with English settlers and made it very clear that the Welsh were not welcome.

The natives were treated as second-class citizens with limited status and rights.

They were banned from the fortified town at night, and only allowed in on market days.

It was a form of legal apartheid in which the English were the masters and the Welsh were an underclass.

The Welsh resented Edward's taxes, they resented being made to pay him homage and they resented not having the same rights as their English conquerors.

But the final straw came when Edward tried to raise Welsh troops for a campaign in Gascony.

Under a new rebel leader Madog ap Llywelyn, Wales would rise up and threaten to destroy everything that Edward had established.

In 1294, they seized their chance.

Madog had raised an army, and across Wales English strongholds were besieged and towns burned.

Edward's ring of stone was being destroyed.

But all of this would mean nothing if the Welsh didn't take Caernarfon.

Caernarfon was supposed to be the impregnable fortress.

After all, thousands of men had worked for 11 years on building it.

But for all its amazing design and its military and symbolic might, there was one problem.

These massive northern walls weren't finished, in part because on this side, the castle was protected by the town walls, but not on market day.

That was the one day of the week that locals could come freely in and out of town.

And that's exactly what the rebels did.

They just marched into the most heavily fortified place in the land and burned whatever they could.

You can imagine how Edward felt about that.

The King was furious.

In December 1294, Edward marched into north Wales at the head of an army of 37,000 men.

(SOLDIERS SHOUTING) Within eight months, despite fierce resistance from the Welsh, the rebellion was crushed.

Madog was imprisoned in London, where he'd spend the rest of his days.

Edward had learned a lesson, and he put all his effort and money into rebuilding the castle.

But he would never see it finished.

Edward I died in 1307 while waging war against Scotland.

He was one of the most powerful and intimidating monarchs ever to wear the English Crown.

By the time Edward I died, Caernarfon Castle was militarily intact and reinforced, looming over the town around it.

But behind the walls it was unfinished.

Apart from Prince Edward's birth, there had been no royal residents, and it didn't have an active military function either.

All the same, what remained was a magical, fairytale castle just waiting for its next King Arthur.

For the next hundred years, a succession of English kings would keep their boots on the throats of the native Welsh.

But the Madog rebellion had planted the seeds of independence, and at the start of the 15th century, during the reign of Henry IV, a new leader rose up to take his place as the greatest rebel hero of Wales.

His name was Owain Glyn Dwr.

Owain Glyn Dwr was an educated man.

He was a lawyer and a landowner.

He'd been in the service of English kings, but he also really understood his own native mythology.

And that's why, when he raised his flag of rebellion here on Twthill above Caernarfon, it was the flag of Uther Pendragon, King Arthur's legendary father.

(READING IN FOREIGN LANGUAGE) Pretty much every culture has its version of the Arthurian myth, the native hero hiding in a cave waiting to rise again.

Today we think of King Arthur as an English hero.

But it's the Welsh who have always regarded themselves as the native Britons, and the Saxons and the Normans as the foreign oppressors.

So Arthur is a Welsh hero, a Welsh savior and a Welsh king.

Owain was appealing to the prophecy that a great man would rise again to lead the British, or in this case the Welsh, against the foreign oppressor.

And that's exactly what happened.

His rebellion became a 15-year national war of Welsh against English.

And he, more than anyone else, would put Caernarfon Castle to the test.

The rebellion began in 1400.

Owain's goal was not just to take Wales back, but to reclaim the title of Prince of Wales.

Glyn Dwr went back to the tried- and-tested methods of guerilla warfare.

He was supported by friends, cousins and local lords.

But what scared Henry the most was the thought that the Welsh were protected by magic, myth, and even King Arthur.

And it looked like Henry was right.

As the war intensified, even the weather seemed to conspire against him.

(THUNDER RUMBLING) Heavy rain caused flooding and broke up his armies.

The very elements appeared to have sided with Owain and the Welsh.

And as if that wasn't enough, in February 1402, a great comet appeared in the heavens, hung around for three months, and for eight days it was bright enough to see even in broad daylight.

That sort of thing was enough to scare the life out of even the toughest medieval mind.

The comet's described in a poem, which says, "The comet in the sky See ye that blazing star "The heavens look down on Freedom's War "And light her torch on high Bright upon the dragon's crest "It tells that glory's wings will rest When warriors meet to die" But to make matters worse for the English, Glyn Dwr had a new and powerful supporter, the king of France.

If Glyn Dwr could take Caernarfon, he would achieve more than just a military victory.

It would symbolize the end of more than a century of English rule in Wales.

It's one thing having God on your side, but it's even better to have the French.

They came to support Glyn Dwr in December 1403.

They blockaded the Celtic and the Irish Seas and they brought the latest military technology to help take the castle.

Siege engines, belfries, and battering rams.

But Caernarfon was no ordinary castle.

The heavy gates where built to resist battering rams.

The high walls, peppered with murder holes and narrow windows were unscalable.

Against the combined might of the Welsh and French forces, Caernarfon's garrison comprised just 28 soldiers.

Astonishingly, that's all the English needed.

So, Stuart, it's 1403, this castle's surrounded by Owain Glyn Dwr's men, all his French allies, but it was defended, the records say, by 28 men.

How on earth could 28 men defend this castle?

If we go up to the tower, I'll show you.

You'll notice that there are no big windows in this castle.

It's all arrow slits, arrow loops.

JONES: All these tiny, little... And you've got all these amazing passages, which you can move from place to place within the castle, unseen from tower to tower, from upper ward to lower ward, completely enclosed and defended, without the enemy seeing your movements.

So they've got no idea, when they approach this castle, how many men are defending it.

They've got no clue.

This is one of the towers that projects out through the main sort of wall of the castle.

JONES: Yeah.

And as you can see, what's really unique about this tower, and in fact the polygonal towers here in general, is the fact that you've got three really large arrow slits, right?

And basically, the guys outside, because of the sunlight and the light outside and the difference of the darkness inside, they can't see us.

So we're totally invisible here.

-We're invisible, basically.

-We've almost got, sort of, well, it's 180 degree kind of range of fire out of here.

That's right, that's right.

So you can defend this whole side just from these three little arrow slits.

Basically, imagine that you've got your attacking force out there.

-Right.

-Yeah?

And I can give you a demonstration of that.

Obviously, we can't use longbows, right?

As much as I'd love to.

But unfortunately, we're surrounded by members of the public now, right?

-But I do have an alternative for you.

-Well, come on then.

So, here's the challenge.

-Okay?

-So this is the modern longbow.

-There is, unbeknownst to you... -I won't point it at you.

...an enemy gathering outside your castle.

JONES: Right, okay.

There are men actually out there gathering.

You are about to be attacked.

-Yeah.

-Okay?

And as the 28 men did in the past, we have to defend this castle.

Well, you'd better grab yours as well, then.

-(LAUGHING) -Right, well, where do we hit first?

We've got three options.

Shall I take that one and you take this one?

Okay, no, I'll take that one, you take that one.

Okay, go for it.

(LASER GUNS FIRING) PRIOR: See them?

See them?

JONES: Yeah, and I think I got one as well.

PRIOR: So, every time you hit them... -Yeah.

-Okay?

One of the sensors on their head will actually flash red.

JONES: Oh, yeah.

Oh, I got one.

Oh no, I think that was just a passing lady, actually.

In fact, it only takes the two of us, really.

PRIOR: To defend this bit of the castle, it does indeed.

All right, get away.

Okay, don't forget, at the front of this castle -you've got water-filled ditches.

-Yeah.

You've also got things like the murder holes in the gateways which you can pour red-hot sand through.

Well, we could clear this place out pretty quickly, I think.

But, Stuart, in 1403, the attackers outside weren't just on foot, they had sows and belfries as well.

What would that have been like?

PRIOR: The walls in this place are so thick that it's just not gonna work.

JONES: So actually, this place is virtually... ...unbreakable?

The only thing that would have brought this place low, all right?

Is a massive trebuchet.

(MAN SHOUTING) Which the records tell us, they didn't have.

So, had they brought a trebuchet, they could gradually have pounded their way through the wall.

But apart from that, it was a lost cause.

So that explains then, 28 men, actually, -pretty easy.

-It's impregnable.

-We could have done it with two.

-We could.

(LAUGHING) Well, it would have been a lot of running around, but yeah, we absolutely could.

Let's go and finish them off, then.

-Okay, let's do it.

-Come on.

(LASER GUNS FIRING) JONES: Twice the Welsh tried to take the castle.

Twice they failed.

Caernarfon really was siege- proof.

Over the next 10 years, the Crown's forces clawed back the territory they'd lost.

By 1415, Wales was back in England's hands.

The leading rebels were dead or imprisoned.

Owain Glyn Dwr refused all offers of pardon.

He was never captured, and eventually disappeared without a trace.

Today, he's a hero of Welsh nationalism.

On a par with King Arthur himself.

Glyn Dwr was eventually cleared as a traitor, but not until 1948, more than 500 years after his rebellion.

But it didn't matter, because by that time, the Welsh dragon had found its way onto the English throne.

For 200 years, Caernarfon Castle in north Wales had been the symbol of conquest and the target of rebellion.

Now, it would bear witness to the greatest sucker punch in British history.

A Welshman was about to seize the throne of England.

Here, just outside the village of Penmynydd on the island of Anglesey, 15 minutes away from Caernarfon Castle, we can find the origins of Britain's most famous royal dynasty, the Tudors.

The Tudors of Penmynydd were three brothers, Rhys, Maredudd, and Gwilym.

They were cousins and close allies of Owain Glyn Dwr and they lived right here in the house behind me.

I guess most people when they hear the name Tudor, think of Henry VIII and Elizabeth I and the Royal Court in London, but not many people know the dynasty started right here in this house, do they?

No, I think that to come to have such a great dynasty founded from Owen Tudor who lived here, born in 1400 here, but the house here actually predates even Caernarfon Castle because we know there was a house here in about 890 and it's even mentioned in a deed in 1221.

And so the connection with Caernarfon Castle here, the three Tudor brothers that were connected with Owain Glyn Dwr, they lived in this house as well?

They lived here, they were his cousins, first cousins, and many people think that they were more instrumental in actually raising a rebellion than Owain Glyn Dwr.

So we know for certain that in 1406 every single person on Anglesey who was a householder was fined for supporting the brothers who lived here.

And that was sort of their ruin for a little while, wasn't it?

The family fell out of favor.

It was their ruin for a number of years, yes.

JONES: The Tudors had picked the wrong side in Glyn Dwr's rebellion, but Maredudd ap Tudor survived, and he had a son, Owen Tudor, who made his way to the English court and began an astonishing upswing in the family fortunes.

Owen's grandson was Henry Tudor, and that meant that within three generations, the Tudors had gone from guerilla warriors to contenders for the English Crown.

The destiny of the Tudors was secured in one of the most divisive and bloody wars ever seen in Britain.

(SOLDIERS SHOUTING) This 30-year conflict, the Wars of the Roses, would end with a great battle at Bosworth between Richard III of York and Henry Tudor, the last hope of the Lancastrians.

On August 7th, 1485, Henry Tudor landed on the southwest tip of Wales and marched across the countryside on his way to a date with destiny at the Battle of Bosworth.

He marched below a flag with the sign of the dragon, casting himself once again as the son of prophecy, the heir of King Arthur back to save the native Britons.

Henry's Welshness was a really important part of his coming back to claim the Crown of England, it wasn't just him saying that he was heir of the House of Lancaster.

He was claiming this ancient prophecy made by Merlin that said that one day this great new king would arrive and fulfill the destiny of the Britons.

And sure enough, when Henry Tudor was crowned King Henry VII, he adopted the Welsh dragon into his royal coat of arms.

From the Tudor years onwards, Caernarfon's military significance began to fade.

Eventually, the castle became more interesting to tourists and historians than to soldiers and invaders.

But the symbolic power of this magnificent fortress would not be forgotten.

In the 20th century, politicians once again began to explore Caernarfon's ancient links to the Crown.

DAVID LLOYD GEORGE: This armament a great idea.

And now here's another thing I want to say.

I'm a free man now and can say what I like.

(PEOPLE CHEERING) JONES: David Lloyd George was the first and only Welshman to be prime minister of Great Britain, and it was Lloyd George who was responsible for thrusting Caernarfon Castle back into the spotlight after centuries of obscurity.

Because it was here in July 1911, that George V's son Edward was invested as Prince of Wales in a mock medieval ceremony that was petitioned for by Lloyd George.

And in July 1969, the investiture of Charles as Prince of Wales again invoked the royal symbolism of Caernarfon Castle.

(MAN SPEAKING FOREIGN LANGUAGE) NEWSCASTER: The gold rod... (MAN SPEAKING FOREIGN LANGUAGE) NEWSCASTER: ...and the mantle.

In giving to the Prince these insignias of office, the Queen could not conceal the gentle touch of a mother.

Despite the formal text of the Letters Patent which proclaimed that Charles Philip Arthur George may have the name, style, title, state, dignity and honor of the Principality of Wales and Earldom of Chester.

JONES: I think this castle still does exactly what it was supposed to.

More than 700 years on it's a physical sign of the relationship between these two nations.

The fierce independent Welsh dragon and the imperious medieval English Crown.

At some point, there'll be a new Prince of Wales invested, we presume, here at Caernarfon, and that ancient relationship will continue.

Another great British moment, played out in a magnificent Welsh castle.