All language subtitles for Britains.Greatest.Bridges.Series.1.1of6.The.Forth.Rail.Bridge.1080p.HDTV.x264.AAC.MVGroup.org.Eng

But, in fact, it's got a lot more in common with the Forth Rail Bridge,

or an agonising death

from what they called 'caisson disease'

and what we call, today, 'the bends'.

One man named George Fowler did die from caisson disease

but, incredibly, there were few other casualties.

125 years later,

similar building techniques are still being used,

albeit with a little bit more health and safety.

On the water behind me here, being built,

is the new Queensferry Crossing,

a £1.3 billion project that's due to be completed by the end of 2016.

Now, at first glance, it may look a lot like

the old grey road bridge just behind it, that it's due to replace.

these briggers could still suffer permanent disability

because they're both cantilever bridges.

And that's not the only similarity with the rail bridge.

In fact, they both used caissons

to dig the foundation in the deep waters of the Forth.

Where are we right now?

Well, we're standing on the top of the south tower caisson,

to the Forth replacement crossing.

You've got a vast amount of concrete, there, before the tower.

So, what actually goes down beyond what we can see?

Below the tower, you can see the top of the foundation.

That's an 11-metre-deep reinforced concrete foundation.

OK.

invented personally by their boss, William Arrol, to speed up the work.

A team of surveyors spent months on a specially-built raft

to determine the correct positions.

Only then could they sink them to the bottom of the firth.

Of course, when your caisson is 70 feet wide

and weighs in excess of 400 tonnes,

it's easier said than done.

Once the caissons were in place, the really hard labour began.

Working in an air chamber just over two metres high,

they'd dig down through tonnes and tonnes of tough clay,

hauling it up, one bucket at a time, through small air locks.

These rare pictures show this hidden sub-sea world.

The huge spades the men are holding is a new kind of jackhammer,

And then below that, we've got the mass concrete

But even with Arrol's new tools, this was dangerous work.

As they dug down,

the caisson would sink further into the riverbed,

with the constant fear that the edge of the caisson

would hit a soft patch of clay, sink too quickly,

and crush the men inside,

or that the compressed air pumps might fail,

flooding the air chamber and drowning the men.

Only when they reached the solid bedrock could they stop.

They would then fill the caissons with rubble and concrete

to create the solid foundations the towers needed.

Even if all went well down there,

At least 70 that we've uncovered with the research.

the bridge remains balanced.

Everything the briggers needed - scaffolding, tools, huge cranes,

even a stove to heat their lunch and a canteen to eat it in -

was hanging off the bridge itself.

There were dozens of trades employed to build the bridge -

labourers, draftsmen, boilermakers,

carpenters and even cooks.

But it didn't really matter what trade you were in,

because when you're 360 feet in the air, it's a dangerous business.

Jenny Meldrum is part of a group of local historians

who campaigned to have a memorial built for the briggers who died.

So, how many men do we think died, building the bridge?

As long as you keep adding sections to both sides simultaneously,

The ages, I can see on here, vary quite a bit.

You've got Thomas Birrell, 59, labourer.

This one sticks out - David Clark, 13.

Yes, he was actually the youngest casualty of the bridge.

Do we know what happened to David Clark?

David Clark, I think, fell from a height on the bridge.

And falling off the bridge - I imagine, he wasn't the only one

to have lost his life that way?

No, no.

Occasionally, people were picked up from the water

but generally, it was a fatal fall, especially at height.

Was that common, then, for kids to be labourers?

to begin.

that goes down to the bedrock.

It's incredible that similar caisson technology

that was used to build the Forth Rail Bridge

is still being used today -

the only difference being that in the 1880s,

they had to climb into the caisson and dig on the riverbed,

whilst nowadays, they dig from above, using barges and cranes.

Digging from above is obviously a lot safer.

But 125 years ago, on the Forth Bridge, that wasn't an option.

By 1886, after almost three years of hazardous, dirty work,

the bridge had a solid foundation,

and it was time for the work on the superstructure above the Forth

and the whole bridge could come tumbling down.

And, once again, they used a method

that the new road-bridge builders are still using today.

It's a really clever construction technique -

something called being self-supported.

Starting from the main towers, the briggers would build outwards.

Every day, they'd add a new section onto the bridge.

They'd build that by standing on

the section they'd built the day before,

that, itself, they would have built

standing on the section they'd built the day before that,

and so on and so on.

The bridge expanded outwards.

What few people realise

Not only would he take on and build these giant projects,

but he'd create machines and tools to speed up the process,

allowing him to cut labour costs and increase productivity.

Arrol's stroke of brilliance

was to turn north and south Queensferry into giant factories.

There were sheds and drill roads for fabricating parts,

offices and studios

for the engineers to prepare plans,

and yards to marshal the hundreds of thousands of tonnes of material

that flowed through the area.

With such a massive project,

there's no room for mistakes,

and Arrol had a trick up his sleeve to make sure there weren't any.

It was this mastery of metal that gave Arrol the edge over his peers.

is that the Forth Rail Bridge was actually built twice.

Every part was fabricated on dry land

and then bolted together to make sure it would fit.

Only then was it dismantled

and taken out onto the Forth itself.

Above all, there were men, or 'briggers', as they became known -

over 4,000 of them in total,

working 24 hours a day, in all weathers.

Some say the whole endeavour

was similar to putting a man on the Moon in the 1960s,

and it's a pretty good analogy -

a seemingly impossible task

But how do you turn this...

and down through the legs of the chair.

And on the bridge, that's the weight being transferred

down through the towers and into the masonry piers.

And that is my full weight being sat there.

It works!

Cracking the design challenges was one thing,

but realising this dream

would not only push the boundaries of technology,

but take a gruelling eight years

and cost many lives.

Now, imagine you're an engineer in 1883.

You've got a brilliant plan to cross this huge span of water.

overcome by engineering brilliance, sheer hard work

..into this?

It was an undertaking unlike anything ever attempted.

55,000 tonnes of steel, 3.5 million cubic feet of masonry,

and more than 6.5 million rivets.

As everyone knows, if you've got a massive building project,

you need a brilliant builder,

and that's exactly what civil engineers John Fowler and Benjamin Baker needed in 1883.

And they found one in William Arrol.

Arrol's skills as a metalworker were obvious from an early age.

Having started as a blacksmith apprentice at 13,

he rose quickly in the trade,

and by the age of 30, he'd opened his own ironworks.

Steel...hook, there.

and the bottom of the tub here

is the riverbed.

So, what they'd do,

they would lower the caisson

down into the water.

Now, because that bottom chamber is full of air,

it would float.

There it is, floating.

And that would enable them to float it

into the position they'd need it,

where, using rubble and water,

they would fill the top compartment.

is representing the Forth,

There we go. That is well weighted down now.

Now, here comes the clever bit - using compressed air,

they would pump air down into the bottom compartment.

You can see the water level slowly going down

as I pump in the compressed air.

And there we have it.

A fully airtight air pocket

at the bottom of the riverbed,

for the men to work in.

Before they could sink the caissons,

they needed to position each one with pinpoint accuracy.

Just a few feet out of line

on dry land at low tide, underwater at high tide.

and a vast sum of money.

In 1890, the bridge cost £3 million to build,

an eye-watering sum of money in those days.

Today, its price tag would be billions.

The briggers' first job

was to build firm foundations for the massive towers,

but there was a huge obstacle they'd have to overcome -

the Forth itself.

Over here, on the north side,

building the piers was relatively straightforward.

Two of them are here on dry land so, no problem.

And the other two are out here, between the tide lines -

The riveters tended to work in teams of four,

A bit more tricky.

But on the south side, the piers are right out here,

in the middle of the firth.

Now, the riverbed is 70 foot beneath me at this point.

And that presents a serious challenge.

So, how did they do it?

The answer is that they used

an underwater building chamber -

a caisson.

A caisson is essentially an incredibly large tin can

that's sunk to the bottom of the river.

Now, this tub of water

But if there's one thing that presents

REPORTER: Britain knows how to respect the courage of these enemy airmen

who fell in the execution of their duties.

(SOLDIERS FIRE GUNS) (BAGPIPES PLAY)

Towards such there can no more be hostility or hatred.

It was the first time Spitfires were in action.

They were scrambled after the attack was already under way,

but they still shot down three of the 12 Ju 88 bombers.

It proved the RAF's new fighter plane

could successfully fend off the Luftwaffe.

(CHILDREN SHOUT PLAYFULLY)

The bridge survived its encounter with the Luftwaffe.

It's survived numerous collisions with ships over the years.

It's survived 200 trains a day rumbling back and forth.

Their coffins were draped in swastikas.

a greater threat than anything else,

it's the Scottish weather.

Now, there's only really one way

to protect a steel structure like this from the elements,

and that's by painting the Forth Bridge -

a process which started

in the final months of construction, back in 1890,

and hasn't really stopped ever since.

And it's not really surprising we've all heard the phrase,

"It's like painting the Forth Bridge",

as there's over 2.5 million square feet to cover.

The painting was so relentless,

They were British bullets.

OK.

And here is the Spitfire, but you can't see the Spitfire,

and I'm down there...

Down there. OK. ..with my little brother.

And the Spitfire is firing all its guns...

Brrrrrrrr!

(GUNFIRE) ..at the bomber.

They were so close, within inches,

it was no effort at all

for me to bend down and pick up the bullets, still warm.

(GUNFIRE)

These bullets were not German bullets!

the owners of the Forth Bridge have maintained a full-time paint crew

So, I would've been killed by what is called now 'friendly fire'.

And did you see what happened to that German bomber...

Yes. ..that was on its way down?

I saw it go like that and then I could see the Spitfire behind it,

still firing at it,

and smoke coming from the engine.

I knew it was going to crash. Mm.

And it, uh, crashed, killing the two young men.

The German airmen were given a full military funeral,

their coffins carried by the British pilots that shot them down.

Movietone News reported the fact

that these young airmen had fought bravely for their country.

when UNESCO, the United Nations Scientific and Cultural Organization,

without actually being in it.

And it's not just the paint that was improved.

The system for applying it has been modernised as well.

The whole bridge is now spray-painted.

Working in sections, the old paint was sandblasted off,

and the new coating was then sprayed onto the raw steel.

But there's a key component that's refused to be modernised -

the rivets.

To get the perfect seal, these still need to be hand-painted,

all 6.5 million of them.

Sometimes, you just can't beat the old methods.

In 2015, the bridge's future was made even more secure

is about as close as you can get to the North Sea

declared the Forth Bridge a World Heritage site.

As long as there are people here to cross this waterway,

this groundbreaking, historic bridge

will now be protected and preserved indefinitely.

The United Nations itself agrees,

the Forth Bridge is an important and unique structure,

not just to the history of Scotland, not to the UK,

but to the entire world.

They declared the Forth Bridge

as a masterpiece of human creative genius.

And you know what? I couldn't have put it better myself.

Captions by Ericsson Access Services (c) SBS Australia 2017

would actually rain down on their cars.

since it opened in 1890,

topping up the famous red paint of the Forth wherever it was needed,

whatever the weather.

And to be fair, they must have got something right

because the bridge is still here.

By the start of the 21st century,

110 years worth of wind and rain,

pollution from steam and then diesel engines,

combined with layer upon layer of paint,

started to take its toll.

People on both sides of the river

complained that occasionally, pieces of bridge

So, try to imagine, that's the bomber, right?

The sheer cost of maintaining it

threatened to overwhelm the bridge's owners, Network Rail,

and people began to think the unthinkable -

was it time for the grand old lady to retire?

In 2001, Network Rail took the decision

to try and save the bridge

by, you guessed it, painting it.

But not just with any old paint.

This time they decided to use a new epoxy glass coating,

which should last for 25 to 35 years.

It was developed for the North Sea rigs,

and I suppose the Forth Bridge

as the nervous designers looked on.

to try and change people's attitude towards the bridge

by staging the ultimate PR stunt.

On the 21st of January, 1890,

two steam trains stood side by side, on the tracks just above my head.

It was the first major test of the new Forth Bridge.

The trains were arranged to see

just how much strain the bridge could take.

Each one had two locomotives, followed by 50 wagons,

each containing 13 tonnes of gravel,

and they had an extra, third locomotive at the back,

just for good measure.

Inch by inch, they crept out across the water,

So, the rail companies decided

The bridge did its job.

Not only did it take the strain of the massive load,

but it convinced a sceptical public

that the bridge was fit for purpose.

For the first time, a passenger could board a train in London

and arrive, in comfort, at Aberdeen, eight hours later,

cutting an incredible five hours off the journey.

But even though they'd proven it was safe and slashed travel times,

there was one controversy that wouldn't go away.

Many leading lights of Victorian society

thought it was just plain ugly.

One New York newspaper said it was

It used pneumatic pressure to squeeze the rivets together,

so very often, it was, if you like, a family affair.

You would have a family unit working,

doing the riveting on the bridge.

Now, this is a steel rivet head.

It used to be somewhere up there,

but it was replaced a few years ago, during renovation work.

They're kind of a glue that hold the whole bridge together.

And up there, there are at least 6 million of them.

With so many rivets,

William Arrol came up with a time-saving invention

to speed up the process.

He created this machine to drive the rivets home.

simply the ugliest thing in the world

saving time and money on the bridge.

By March 1890, the bridge was all but complete.

The Prince of Wales, the future King Edward VII,

used a specially adapted Arrol riveting machine

to force the last rivet home,

assisted by William Arrol himself.

Despite the enormous achievement this structure represents,

some people weren't sure about it at all.

They weren't sure they liked the look of

this great hulking piece of red steel

stretching out across the landscape.

But more importantly, they weren't sure it was safe.

for their bombing runs.

But the truth is we're incredibly lucky it's still here at all.

On the 6th of October, 1939,

Britain had been at war for just six weeks

and, at that stage, it was an affair taking place far from these shores.

But on that morning, something appeared

out of the skies from the east.

(AIRCRAFT ENGINE ROARS)

It was the first bombing raid on British soil,

the primary target being the Royal Navy fleet

anchored out in the Forth.

But the bridge was a secondary target,

and the Luftwaffe used it as a navigational marker

has carried millions of passengers across the Forth.

Richard Demarco was just nine years old back then.

He was playing on the beach a few miles downstream from the bridge,

where he witnessed one of the first bombing raids

of the Second World War.

DEMARCO: It was October,

a beautiful day, cloudless sky,

and then, suddenly, I noticed little white clouds appearing,

that were accompanied by a dull thud.

That was the sound of the shell exploding.

Anyway, I wasn't worried, but I thought how beautiful they were.

But I was slightly more worried

with the sound of the Spitfire, that I couldn't see, on the tail.

The bridge wasn't going anywhere.

and the only way to improve it

was to hang the designers from the highest girder and dynamite it.

But the designers knew it wasn't beautiful. It wasn't meant to be.

It was meant to be solid and it was meant to be strong.

They didn't care what it looked like.

In fact, despite the criticism over the bridge's looks,

it became an instant tourist attraction.

Baker, Fowler and Arrol had done it.

They had bridged the unbridgeable Forth,

convinced a sceptical public that it was safe,

and had opened up the north of Scotland

for trade and passengers alike.

all of my weight is being transferred between those members

Its iconic structure quickly became a symbol of Scotland

and as the years went by, it became a much-loved neighbour and friend.

(TRAIN HORN BLARES)

But fame has a downside.

When the Second World War broke out,

the Forth Bridge became something new -

it became a target.

The Forth Bridge took eight years to build

and cost the equivalent of billions today.

But in 1890, the largest cantilever bridge in the world was finished

and over 125 years later, it's still standing.

This amazing bridge

became clear for all to see.

It was supposed to support a giant tower for a huge suspension bridge,

but they never got past that point

because a month after construction started, disaster struck.

(WIND HOWLS)

On the night of the 28th of December, 1879,

a fierce storm raged over the Firth of Tay.

At approximately 7:15 that evening,

a train set out along Bouch's new Tay Bridge,

heading north, to Dundee.

The bridge collapsed, and the train, along with all its passengers,

was sent plummeting into the dark icy waters beneath.

It wasn't until daylight the next morning

that the true extent of the disaster

sits on one of the foundations built to hold Bouch's bridge.

Part of the bridge had literally disappeared.

The Tay Bridge disaster shocked the world

and its ramifications can still be felt today.

In the McManus Galleries, in Dundee,

they have a chilling reminder of that fateful moment.

I'm very fortunate - I've been granted access, here,

into the archives of the museum,

to see some items related to the bridge disaster

that aren't normally on display.

And a lot of these here were found on the beaches of the Tay -

items that were washed up after the disaster -

and one, in particular, of note.

It was such a success,

the locals assumed it would be the answer they'd been waiting for.

Little did they realise it would soon turn into a nightmare.

In 1871, Thomas Bouch,

one of the most successful and renowned engineers of the time,

started construction on a bridge

across the first of the great firths, the Tay.

It took seven years,

but by 1878, the bridge was complete.

It was a slim, elegant, largely cast-iron bridge,

almost two miles long,

towering 88 feet above the water

and carrying a single railway track.

It's at the back here, it's a pocket watch

Queen Victoria made the journey up from London

to witness the bridge for herself.

And she must have been impressed

because Bouch was awarded a knighthood for his efforts.

But more importantly,

he was given the chance to take on an even bigger challenge -

to cross the Firth of Forth.

If he succeeded, it would be the pinnacle of his career.

Plans were drawn up

and a year after the Tay Bridge opened,

construction started right here.

In fact, this wee lighthouse

the Forth Bridge.

Because of his perceived failure, here on the Tay Bridge,

Thomas Bouch was sacked by the railway,

work on his Forth bridge was abandoned

and less than a year later, he died, a broken man.

It looked like rail passengers

were going to be stuck with the dreaded old ferry from now on.

But back in London, two engineers had come up with

a new and daring plan to cross the Firth of Forth -

a design so radical and at a scale so large,

it had never been tried anywhere in the world.

If it worked, it would change the way we build bridges forever.

This is one of the truly great engineering wonders of the world,

are a few foundations in the shadow of the bridge built to replace it.

It's actually quite intimidating, being stood under here.

I'm so close, under all these thousands of tonnes

of steel girders and truss work and all the rivets.

And looking along, it's just a real mishmash of steel everywhere.

I'm about to go through this gate,

and I'm very privileged to be doing so

because normally, this area is restricted

to maintenance crews only.

Standing here, you get the feeling that this is a bridge like no other -

a bridge that flaunts its strength in a thousand beams and girders.

It's actually hard to make sense of it all.

So, why does this bridge have such an incredibly complicated structure?

saying he hadn't designed the bridge sufficiently

from one of the firemen in the locomotive on the train,

and it's stopped at the time of 7:31 and 37 seconds,

a few moments after the bridge went down.

It's a real marker for a moment in time.

At least 74 people died that night,

but as there was no accurate record

of the number of passengers on the train,

the true number will never be known.

Designer Thomas Bouch blamed the train,

saying it must have derailed

and as it veered off the side, it pulled the bridge down with it.

The official inquiry into the disaster blamed Bouch,

it was time to bridge the firths,

to withstand those gale-force winds that blew that night.

Unfortunately, we'll never know the exact cause,

but everyone agrees one thing made it worse -

this.

Cast iron.

Bouch's Tay Bridge was designed

so the entire structure rested on a series of slender pillars,

each one made of cast iron -

a material he was going to use on his Forth rail bridge too.

Nobody suspected that the very metal itself

would prove to be the bridge's downfall.

Today, all that remains of the original Tay Bridge

When it opened in 1890,

(TRAIN HORN BLARES)

(CHUCKLES) Here we go.

Look at that!

You look down the middle from here,

it's this endless crisscross of steel all of the way along.

This is amazing.

Oh, yes!

The amount of bracing's incredible.

That was absolutely brilliant.

For over 1,000 years,

bridging this body of water was considered an impossible dream,

until a team of Victorian visionaries came up with an audacious plan.

but there's one view that very few people ever get the chance to see.

it was one of the longest bridges in the world.

It pushed the boundaries of technology

and changed the way we build bridges forever.

But it almost didn't happen.

(PLAYS LIVELY TUNE)

The journey from the centre of Edinburgh, here,

across to Fife, on the far side, the north side, of the river,

takes about half an hour these days,

thanks to the Forth Rail Bridge.

But if I'd have been attempting that journey back in the 1870s,

it would have been a very different story.

Back then, railway-mania was sweeping the country,

I'll uncover the huge egos, flawed geniuses and jealous rivalries

spanning our most dramatic landscapes,

have not only linked our island, but made it great.

These are the bridges that are known around the world,

built by visionaries like Stevenson and Brunel,

who are famous even today.

Look at this!

From the banks of the Tyne to the mighty Thames,

from the Firth of Forth, to the Menai Strait...

..I'm on a journey to discover how those great bridges were built.

Here we go.

..and the sweat and sacrifice that went into their construction.

Stopping traffic.

with lines spreading

behind their creation.

It's as if he'd been airbrushed from the whole story.

These are Britain's Greatest Bridges.

The Forth Bridge -

a mile and a half long, 361 feet high

and more than 125 years old.

Weighing over 50,000 tonnes

and sitting on 640,000 cubic feet of granite,

it dominates the skyline,

as it marches across one of the deepest estuaries in Scotland,

the Firth of Forth.

It is, without doubt, one of the most iconic bridges ever built,

you can get very large, difficult waves.

And it feels so close,

but at the same time, very, very far away at the top.

Wow!

This is the only way to see this bridge!

Len Saunders, a local engineer,

has been rowing these waters for over 30 years.

So, Len, we're doing well today

because the weather gods are very much with us.

But it's not always as plain sailing as this, is it?

You have to remember the tides here are very strong.

You get strong winds.

If you get the wind against the tide,

this experience I'm having with the bridge here, now.

But...but people would still do it, would they, in all conditions?

Well, it depends how desperate they were.

Right.

If you had to make a journey,

could you afford to go by road, 60 miles round,

or did you risk it on the ferry?

And, of course, there was not only the weather to worry about.

Yeah? But the actual ferrymen.

They were a bunch of rogues,

and they would threaten to land you on the Island of Inchgarvie,

if you didn't cough up more money for the fare.

So, when the train companies decided

the Firth of Tay.

the length and breadth of Britain.

By 1850, there was a fast connection to Edinburgh from London,

more than 350 miles to the south.

But Edinburgh was where it stopped.

Anyone wanting to go further north from here faced a problem.

Well, two problems, actually.

Firstly, the Firth of Forth out there -

an enormous river estuary,

over 60 metres deep in places.

That's deeper than many parts of the North Sea.

And then, about 50 kilometres further up the line,

a second huge estuary,

Well, to answer that, I need to get a different view -

Both these firths

have been stumbling blocks for travellers for centuries.

For over 900 years, this is the only way people could cross the Firth -

in a sailboat, if they could afford it,

or a rowing boat, if they couldn't.

Twice a week, a team of locals take to the water

to carry on the traditions of the ferrymen.

They've agreed to take me out for a little pleasure cruise -

well, pleasurable for them, anyway.

I mean, this is absolutely spectacular.

And because I'm in a rowboat,

it feels almost more intimate, more personal,

of their design.

So, it's perhaps ironic

that the country's greatest engineering landmark

was designed by two Englishmen -

Sir John Fowler and Benjamin Baker.

This is a portrait of Fowler,

the youngest ever president of this place,

the Institution of Civil Engineers.

And Baker, the other half of the engineering partnership,

can be found in the institution's main library,

hanging just behind me.

To bridge the seemingly unbridgeable gap across the Firth of Forth,

Baker and Fowler came up with a radical new concept,

and these are some of the original blueprints that were drawn up

Thomas Telford, James Watt, John McAdam, to name but a few.

Instead of a suspension bridge or a viaduct,

they had decided to build a cantilever bridge.

So, what is a cantilever?

Very simply, it's a structure that's only attached at one end,

while the other end extends out into space.

Cantilevers are everywhere.

Aeroplane wings, awnings, diving boards,

even some chairs are cantilevers.

To build a cantilever bridge, you actually need two cantilevers,

often called arms.

One on each side of the water, reaching out towards each other.

And then, if necessary, any gap in the middle is closed

So, what form should this new bridge take?

whipped in from the North Sea.

The normal Victorian solution

of a viaduct running low across the water

could solve all of these issues.

But there was another problem.

The Firth of Forth was, and is, a major shipping channel,

so the bridge would have to be tall enough

to allow ships to pass underneath.

The Tay Bridge fell apart

trying to overcome this exact problem.

Each of its piers were too tall

and the middle spans were too long.

using a third section suspended between the other two.

Thomas Bouch, designer of the Tay Bridge,

had actually planned to build a huge cast-iron suspension bridge,

a bit like the Forth Road Bridge just along the river.

Technically, it was possible,

but no-one had ever built

a suspension bridge of that length before.

And many people thought a design like that would just be too flimsy

and, more importantly, it would LOOK too flimsy,

so that idea was ruled out too.

The solution for bridging the Forth

was to be found at 350 miles away, in London.

Scotland boasts a long line of famous engineers -

the anchor, the ballast points.

and in between them, their Japanese engineering student, Kaichi Watanabe.

This famous picture

convinced the railway company and the public

that this bridge would stand the test of time.

Now, there's no magical trickery involved in this demonstration.

It's just simple physics.

And I'll show you, by sitting on this platform, here.

Now, if this goes well, this should take my weight.

Everyone alright?

That's taking my full weight, there.

So, let me explain what's happening.

The two gents on the end are representing

Fowler on the right,

And my two colleagues here

are representing the towers of the bridge.

Now, their arms

act like the top cantilevers of the bridge.

Now, they're in tension

when I put my weight on here.

There we go.

And our wooden poles here,

they represent the bottom cantilevers to the bridge.

They're in compression, they're being squeezed

and when I put the weight on this middle platform here,

that's suspended between the two,

supporting three giant 361-feet towers.

Baker and Fowler didn't invent the cantilever bridge.

It's been used all over the world for hundreds of years,

but never on the scale they envisioned.

One of the biggest advantages of this type of bridge design

is that you can build outwards from each bank,

without having to face the difficulties or the dangers

of erecting temporary scaffolding in deep or fast-flowing waters.

So, in 1883,

four years after work stopped on Bouch's suspension bridge,

they finally had a solution for crossing the Firth of Forth.

Massive granite piers, 71 feet across,

would be secured on the riverbed,

one that could cope with winds that can easily top 90 miles an hour,

The towers would support immense cantilever arms,

connected by short bridging sections.

The ends would connect to two smaller viaducts,

either side of the bridge.

When finished, the bridge would be over 8,000 feet long,

weigh over 50,000 tonnes

and be held together by 6.5 million rivets.

To prove to the world

that their solution would work,

they created this extraordinary demonstration,

a human cantilever.

That's Baker on the left,

and different interconnecting parts.

that run between the top of the towers,

like a huge rollercoaster,

taking the weight as the trains roll through.

The towers carry the weight

down to the masonry piers,

which hold the whole bridge up.

All those small ties

basically prevent the whole thing pulling apart

but, at the same time, they add stiffness

so it doesn't twist in the wind.

It seems almost too complicated,

with its strange angles

The rail track below me is hanging off these flat girders

A more pared-down structure would have made more sense.

So, why did they design and build it like this?

The reason it seems so over-engineered

is because, well, it is,

and for one simple reason -

the Tay Bridge disaster.

The memory of that tragedy is encoded into the DNA of this bridge.

The design, the materials, even the methods they used to build it,

were seen as a reaction to that tragedy.

This bridge not only had to physically stand up to

whatever the world could throw at it,

it had to make people believe it could do so.

You've even got snow on some of the mountains up here.

from right on top.

It's a 361-foot ride up the north tower, to the top.

My guide, Colin Hardie, is charged with maintenance on the bridge,

and gets to go up every day.

But for me, it's a chance of a lifetime.

(LAUGHS)

Phew! Look at this!

The views from up here are absolutely stunning.

I mean, you've got...

You've got the city of Edinburgh just behind us, there,

and then you're just heading up,

straight out, into the mountains, up here.

It was designed to combat fear.

And you can see the other bridges right beneath us,

where it feels like you're on top of the world, up here.

It's magical.

As Colin gets on with making sure

the bridge is still here for another 125 years,

I get to take a look at this amazing structure

from a totally unique perspective.

I'm stood now, looking down from the top of the bridge.

All of that intricate, cross-bracing metalwork

starts to make a bit more sense.

There's a...there's a lot of order and form to it.

This is built to be strong, it's built to last.

to use on such a large scale.

for the failure of the supports on the Tay Bridge.

Now, if we look at steel, by comparison,

it's relatively strong in every direction.

So, nice steel beam there.

Admittedly, that's a slightly thicker steel beam,

but...I've got a much bigger hammer.

(LAUGHS) That's done absolutely nothing at all to that,

and that's why they built the Forth Bridge out of steel.

Steel is basically iron

which has had its impurities, like carbon, reduced,

making it stronger and less brittle.

It had always been prohibitively expensive

And it's that fundamental weakness that was blamed, in part,

But in 1856, a new discovery -

blowing air through the molten iron to burn off the impurities -

meant that they could now produce vast amounts

of high-quality steel cheaply,

making it the perfect material for building the Forth Bridge.

But using steel didn't solve everything.

The bridge still had to overcome some major problems -

firstly, the great distance from shore to shore,

over a mile and a half,

the incredible depth, sinking down almost 100 feet,

and, of course, they had to come up with a solution

for the Scottish weather,

to build such large supporting structures from.

To help counter this fear

and settle the nerves of a shocked public,

the decision was taken to build the new bridge across the Forth

out of a completely different material to the Tay Bridge -

steel.

(FORGE HISSES AND ROARS)

To help understand the advantages of steel over cast iron,

I've travelled to London,

to one of the last traditional cast-iron makers.

The Tay Bridge wasn't the only bridge to be made out of cast iron,

but it was the bridge that clearly and tragically demonstrated

why it's the wrong material

Britain's iconic bridges,

Cast iron is a very strong material.

If I take this spindle here, this cast-iron spindle,

and use it as a pillar -

just rest it up there -

I can apply huge amount of force

on the top of there...

I could be hitting that all day long.

It's not gonna buckle, it's not gonna break,

when I'm applying a force in that direction.

But try and bend it

by hitting it like this and...

That went through really easily.