Of all the great feats of engineering that have helped to shape Britain,
there's nothing more dramatic
than the medieval castles of north Wales,
built over 700 years ago by Edward I to stamp his authority on his newly conquered province.
They are some of the finest castles in the country -
one of the greatest feats of royal engineering in British history.
This week, I've come here to find out how a Frenchman and an English king
completely changed the art of castle building for ever.
In 1282, the Welsh prince, Llewelyn ap Gruffydd, felt strong enough
behind his walls at Dolbadarn and Dolwyddelan
to defy English authority and assert his independence.
It was a situation King Edward I refused to tolerate.
And he was determined to obtain Llewelyn's submission by force of arms.
Campaign Wales wasn't going to be as easy as Edward had imagined.
The whole place was heavily wooded,
and it took 2,000 men to clear a path through the woods for Edward's armies.
Edward fought two very hard and violent wars in Wales.
He finally won when Llewelyn got killed in a minor skirmish.
He were determined never to have to fight the Welsh again.
He decided on Europe's most ambitious medieval building programme.
Like the Normans before him in England, he would subdue the Welsh with castles.
Work started on three castles - Harlech, Caernarfon and Conwy.
But it wasn't just castles that were built.
At Conwy and Caernarfon, the castle was put into a walled town -
an idea borrowed from Gascony in southern France, where Edward had been Duke.
That isn't all Edward borrowed from France.
All these castles in Wales were built by a Frenchman called James of St George.
Master James of St George came from St George D'Esperanche in Savoy, which is where he got his name.
He came up with a design for a whole new style of castle while working as the king's architect.
To understand the great advances he made in castle building and design,
we start with a castle the Normans had built in England 150 years earlier.
Even back then, the French built the best castles.
This is Hedingham Castle in Essex.
It was built for a Norman lord, Aubrey de Vere, in the 12th century.
Aubrey wanted to make his castle look posh,
so he put an outer skin of dressed stone on it,
to impress his friends and maybe his enemies too.
You see it's quite thin, really.
There's no headers in it, no nothing.
In fact, it gives a false impression.
It almost looks as though the Victorians did it, it's so neat and tidy.
Really, you get a better idea of what holds the place up downstairs in the undercroft.
Here I am, down in the undercroft.
Here, really, you can see what's holding the whole thing up.
Not a lot, eh? It's really the mortar.
There's more mortar than there is stone, actually.
Really, it's a credit to the men who mixed it.
It's still quite solid after all these hundreds of years.
There must have been more mortar mixers than stone fixers.
It looks as though they put the outer skin on the outside, which is beautiful dressed stone,
and then they built 18 inches of pebbles and flints,
then chucked the mortar in and, as they did it, threw the stones in.
You can also see, down here, a great pillar that's 14 feet square.
It goes all the way up to the arch above and takes the thrust of the whole weight of the building.
In fact, the castle is built round a huge arch right up its centre.
This is a cross-section of Hedingham Castle keep.
As you can see, most of it's arches.
For these arches to stand up, they've got to have something substantial to spring off.
Unlike a normal bridge, you need plenty of meat on each side to take the thrust of the arches.
Down in the undercroft, which is equivalent to the cellar,
the walls are actually 14 feet thick, with all this weight of arches pressing on them.
Then you've got the weight of a floor,
plus the knights and noblemen round a great table, eating venison... You don't want it falling in.
The arch over the banqueting hall is the biggest Norman arch in England,
something like 28 or 30 feet across.
This worthy, great arch emerges out of the wall.
You don't really appreciate the arch until you look at the great expanse
of the floor above.
If they hadn't built it, they'd have had to search around for a tree 50' long and 2'6" square.
I rather think it were easier to do the arch than find such a tree.
A keep like this is very sound. The solidity of its structural work can't be faulted.
You can see how thick the walls are all the way to the top.
So when Master James came along with his new ideas, it wasn't the building techniques he set out to improve.
It was the overall shape of the castle and its outer defences.
Until this time, the keep had formed the heart of the castle.
It housed the lord of the manor and was built on a mound of earth called a motte.
Next to this was the outer stockade, where everybody else lived, called the bailey.
The bailey had a wall round it with a gate in it.
So the gate was the weakest bit.
If you knock the gate down, the enemy were in and the defenders had to hide in the keep.
What Master James did was to move the keep to the gate, and rechristen it the barbican.
What he did next was to do away with the motte altogether
and build a series of towers round the outer wall, to make the castle more defendable.
If you did breach the walls or gain entry through the barbican,
you could be fired at internally by the defenders on top of the walls
and in each of the towers.
You could see this at the first of his castles, which was Harlech.
It's the most defensive of Master James' works - hardly surprising,
as they started it when Edward was still at war with the Welsh.
This side of the castle, without a doubt, is the best side to show the various stages of construction.
It's very obvious, if you look at the main wall, you can see at the bottom
that it's quite rough stonework, done by the soldiers while still under attack.
When they had more time, and a bit of protection from the bottom wall,
they completed the top 25 or 30 feet in a much better fashion. Better stonemasonry and everything.
Last but not least, the bastion and the curtain wall, or outer wall,
will be built at a later date as an extra form of defence.
If the enemy did approach, they could run and leave their trowels for next time.
The key to the success of the castle is this staircase,
which rises 200 feet from the sea.
Well, it did do, before the sea receded over there.
It didn't really matter if the Welsh held siege on the front, or the land side of the castle.
Supplies could be brought in by boat,
so they could keep the Welsh at bay for ever.
This staircase must have had an army of men carrying bags and all sorts of things.
And I rather think, by the time they got to the top,
they'd be a bit knackered.
Without a doubt. I think that's why this plank's here for sitting on.
From this angle, you can see how the rock had to be dug away to set the castle foundations
directly on to the solid rock.
It's as if the castle was hewn out of the rock itself.
Having built the castle on top of a large cliff overlooking the sea,
this left the inland side of it rather vulnerable to attack.
To remedy this serious problem, they dug this huge gorge behind it in solid rock.
Using the natural cleavage of the rock, and iron wedges and big hammers,
they shifted immense amounts of material.
Without a shadow of a doubt,
it's a wonderful feat of engineering and rock removal.
CLANK! And this is how they did it.
They got a hammer and some form of a drill
and then they proceeded to drill a hole in the rock.
When the hole's sufficiently deep, you then insert a pair of slips. Some people call them feathers.
Two lumps of iron down the hole.
And then a big iron wedge, which you insert between the two metal plates.
And this, of course, has a nice sliding action when you beat it with the hammer.
It opens up a great crack and off will come a great slab of rock.
Hopefully, we'll get a big lump.
As you can see, it's not as easy as it sounds.
I've not brought a big enough hammer!
I don't know about building a wall, but there's a few slates for me roof!
That were partially successful, but I think they'd have had bigger and better tools than what I've got.
I still wouldn't like to do that all day long - would you?
Very detailed records were kept about the construction of these castles.
At the Public Records Office, David Carpenter tells me all about them.
This is the account of the comptroller, the person in charge of the money at Harlech,
for 1286.
It tells you the numbers of people working, the different rates of pay.
In the margin, it tells you who the craftsmen are, with these lines.
"Cement" - masons. "QRR", quarriers. People digging the great ditches.
My namesakes, the carpenters. Then the smiths.
This is where I would be. Not you, Fred. The minuti operari - the labourers.
How much money did they get? It tells us that.
It's very, very, variable rates. Someone skilled, like you, Fred, might get three shillings a week.
Shall I pay you? Yeah! I'm the comptroller. Let's scatter some 13th-century money around.
How much do you think you're worth? I'm a top-rank mason!
Sure you're not one of the labourers? I made six stones today.
If you were a labourer, you'd get one of those. Possibly a half.
But you're better than that? Oh, yeah.
Fivepence a day. Thank you. Don't spend it in the Harlech pubs.
Would there be an ale allowance as well? I fear not.
Actually, that's the fascinating thing. This is very valuable. That's the only currency.
You couldn't actually go into a pub and buy yourself a drink,
because the money's worth too much.
You'd probably have to do that by barter.
I suppose from this document, you can tell how many men at any period in time worked on the... You can.
This is very seasonal building work. I suppose then as now.
If we go to when this roll was begun, in a very cold January,
there's only one mason working.
He seems to be doing a sort of special job.
And then suddenly - Sunday 21st April -
to Philip Rum and Thomas del Meded, with 29 masons,
and then their pay - suddenly a gang of masons has arrived under Philip Rum.
That's only the start of it. If we go to July... Spring and summer.
You've got 225 masons working, so it's gone up by about 200.
Another thing to think about is the constant threat of the enemy.
Absolutely. Once they'd got it up so it could be defended, they could go off
and do one somewhere else.
In this very tense period, you get workmen being moved under armed guard.
Very dangerous. If I was a workman, I'd be pleased to get out of it
and take my little pouch of money home and get back to where I'd come from.
The most impressive of King Edward's castles was Caernarfon,
because here, what he built was more than just a castle.
Edward decided Caernarfon was going to be the centre of his administration in Wales,
so the castle would be his royal palace -
a symbol of English dominance over the Welsh he had defeated.
Caernarfon is built on a spot close to the old Roman fort of Segontium,
which had connections with the famous Roman emperor, Constantine,
who were a bit of a rebel, because he captured the Roman empire with a British army,
and was responsible for building the city of Constantinople.
When Edward decided to build Caernarfon,
he got Master James, his chief architect, to mimic the stripes on the walls of Constantinople.
The castle would be HQ of his English empire, right in the place where the Romans had theirs.
Work began here in 1283, when Edward was still at war with the Welsh.
Here once stood a row of houses
and it took 20 men a week to get rid of the timbers and the debris.
But they still made a mistake.
They only brought the walls up at this point to about 20-odd feet.
Edward relied on the strength of the town walls to keep the enemy at bay,
but in 1296, the Welsh broke through.
Of course, this business of 24 foot here were really no opposition to 'em at all.
They soon gained entry.
Once the revolt was put down,
they increased the height of these walls and the King's Gate was built to guard this entrance.
Over here, on my left, is all that remains of the once Great Hall.
If you look closely, you can see the holes where the roof timbers were,
and then, round this corner,
a lovely plinth or skirting board at the outer edge,
which would have followed the bases of the buttresses round the corners.
I suppose there'd be a lovely window frame in the middle.
Really, once, this particular bit must have been a beautiful building.
It's now gone. It's rather sad, in a way.
The layout of the castle was not the only defensive feature that Master James designed.
As you can see, in between these two towers is quite a short length of castle wall.
This wouldn't have been able to be defended by single arrow loops.
Master James came up with an ingenious solution.
These are like three entrances all into one.
So if you imagine three crossbow men,
one here firing that way - twang! Another one up here - twang!
And another one here - twang!
It'd be like all that crossfire down below.
The enemy looking up at the walls would think that between the two slots, he'd be safe.
But he'd get caught in deadly crossfire like a medieval machine gun.
But to really understand the castle's defences,
you need to go up the Eagle Tower.
From up here, on top of this tower,
you can really see how Master James' defences worked.
On that side, we've got the sea,
and over here, we've got the river, deep and wide,
which would have kept the enemy at bay for some time.
Then we've got the castle itself, which has two lines of defence.
It once had a great wall across the middle, which has been knocked down, so it was two castles, in a way.
Then, round here, there's the town wall, which follows the shoreline,
and then turns right, inland,
and once upon a time, connected with the castle over there.
It'd be a heck of a place to take.
Caernarfon took nearly 20 years to build and, at nearly £20,000,
was the most expensive of Edward's Welsh castles.
The total cost of them all was over £78,000,
but his wars there had cost £103,000, so they seemed a good investment.
Even so, the cost of them, coupled with Edward's wars in Scotland,
was making a bit of a dent in his finances.
There's nowhere better to see this than just across the Menai Straits on Anglesey.
This is Beaumaris, and its design is the most technically perfect in the whole of Britain.
It would have been Master James' greatest masterpiece,
but the king ran out of money and couldn't afford to finish it.
Like Caernarfon, it has layers of walls within walls,
but unlike Caernarfon, it's perfectly symmetrical
and the whole site is surrounded by a moat, filled with a controlled supply of tidal water.
This was the state of the art of the 13th century.
There are no less than four successive lines of defence built into this castle.
Even if you did battle your way over the drawbridge and then under three sets of death holes,
people pouring boiling hot tar down into your chain mail, and you arrived here,
this were just another death hole but bigger - arrow slots everywhere.
You've got to fight your way through and they'd be raining down on you like red-hot bloody knitting needles.
Finally, you went round this corner here,
and you've got the same thing again!
If you survived the drawbridge and the first set of murder holes, various doors,
and you got here and didn't look like a pincushion,
there was yet one more great door with six-inch-square bolts of oak behind it.
Just four foot further in, there was a portcullis, possibly made of iron with great rivets through,
and then - God forbid - another four sets of murder holes,
and then another door, another portcullis and another door.
I don't think anybody could ever get through. You'd have a job doing it with a tank!
But it's not until you enter the heart of Beaumaris
that you get an idea of the sheer scale of its defences.
If you got this far, which I very much doubt you would,
you still wouldn't be able to get at the king,
because the rest of the soldiers would be round the walls, and more arrows raining down.
So you'd still not won.
You had to cross the centre and take the building with the king in it.
In fact, the castle was surrendered twice in its history, but never taken by any form of assault.
The scale of Beaumaris is incredible.
Through the gates of its protected armour,
over 2,000 men shifted more than 32,000 tons of stone,
they mixed more than 2,000 tons of lime mortar,
and nailed over 100,000 nails into more than 3,000 boards.
All that was done in just one year.
When James of St George and the king built these castles, spirit levels hadn't been invented.
If you look at the moat and the joints of the masonry, it's perfectly level with the water.
There wouldn't be water there when they built it.
All they had a was a stick with a piece of string, with a lead weight on the end,
and a hole that received the lead weight,
and a line drawn up the middle.
Put it on the wall like that, and if the wall is plumb,
the lead weight will hang perfectly central in the hole.
If it leans, of course, the ball's in the wrong shop.
That's how they got everything vertical.
Compare it with a modern spirit level, and, of course, it's perfect.
We've not improved that much, really, have we?
This, behind me, is all that remains of the once-grand gatehouse, you know, the inner gatehouse.
Charles II issued orders to demolish it.
He didn't get so far.
He got the top bit off OK, but I think they must have give up. They had no dynamite in them days.
In a way, he did us a favour, because he's shown us how the wall was really built.
There's beautiful dressed stones on the outside with nice narrow joints,
and in the middle, it's just big lumps of all sorts thrown in with a great deal of mortar,
but there's no real voids in it.
Over the back here, there's two lines of inclined holes,
which would have contained the put logs with an inclined plane.
As the wall grew upwards, they left a stone missing, stuck a piece of wood on to the top of the wall,
tied a tree trunk to the other end and put boards across,
to enable them to raise materials to the top of the wall as it advanced upwards.
They had cranes, but they were slow and wouldn't have delivered the necessary amounts of materials.
So they devised the inclined plane, where maybe two or three men
could drag a boxful of mortar up.
I still use basically the same methods today.
Much easier to drag a heavy weight than it is to lift it up and carry it.
You'd have to get a crane or a helicopter, nowadays, to get something high up.
If it's a reasonable weight and can be dragged on some sort of sledge, it's a lot cheaper.
Might be a bit slower, but it still works.
Beaumaris was never finished.
It was so incredibly expensive, the king simply couldn't afford it.
When you look around and see the amount of chambers and staircases,
compared with the other castles,
you can see the reason why.
It never really got any further than this level here,
and that were 20 years after the king had died.
The king died in 1307, closely followed by James.
Beaumaris is a monument to the great dreams they had.
They both had the ideas of grandeur, but not the money or the time.
That's the reason, really, that the thing's unfinished.
Time and tide waits for no man - not even the king.
But together, they built something that changed the face of Britain.
And in the castles of Edward I,
Master James of St George has left us with some of the most impressive structures in the world.
They also heralded more peaceful times.
Next week, I find out how the castle gave way to the country manor house,
as the violent days of the Middle Ages came to an end.
To find out more about the building of Britain, visit the website:
Subtitles by Veronica Wells BBC Scotland - 2002