All language subtitles for puorGVM.CAA.462x.VTDH.p0801.egdirB.ainnatirB.ehT.6fo4.1.seireS.segdirB.tsetaerG.sniatirB

Britain's iconic bridges,

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 Stephenson 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 constructions.

Stopping traffic.

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

behind their creation.

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

These are Britain's Greatest Bridges.

Britain's great bridges
changed our country,

shrinking distances
and boosting trade.

But there's one bridge that
not only changed Britain,

it changed the world,

and it's a bridge that
you may never have heard of.

This one -
Robert Stephenson's Britannia Bridge.

Opened in 1850, this game-changing
wrought iron bridge

had a span of over 460 metres
and weighed more than 4,500 tonnes.

It was built to cross
the Menai Strait,

a dangerous tidal channel
between North Wales

and the island of Anglesey -

a stretch of water so hazardous

that even Admiral Nelson
was said to fear it.

Sadly, much of what you see today
is a rebuild.

A lot of the original bridge
was lost to a devastating fire.

The first Britannia Bridge
didn't have these magnificent arches.

In fact, it didn't even have a road.

It was just a rail bridge,

constructed using
a straight wrought iron beam

supported by three great towers.

And it's that beam which made
the Britannia Bridge so special.

But why?

Well, it's the way it was built,

using this unlikely-looking
lump of iron - the box girder.

Unglamorous as it may appear,

this small piece of
what was once a giant, long tube

is one of the most
important advances in engineering

in the last 200 years.

It changed the modern world
in ways that Robert Stephenson,

the designer of the bridge,
could never have dreamed of.

Your car, your TV,
the sofa you're sitting on,

perhaps even your clothes,

there's a good chance
they were transported

across the globe in
a giant floating box girder...

because it was this innovation,
pioneered on the Britannia Bridge,

that helped us to build
the huge cargo ships

that crisscross the world's oceans,
in effect shrinking the planet.

Today, box girder technology
is everywhere,

making even the most unexpected
structures a reality, like this.

The Infinity Bridge
here in Stockton-on-Tees.

Just look at it.
It's fantastic, isn't it?

It kind of flows and skips
across the water.

And call me a geek,
but as an engineer,

I love a structure like this
because it does its job.

It's robust and it gets people from
one side of the river to the other,

but it does it with grace and style.

Visually, it's about as far
as you can get

from the Britannia tubular bridge,

but at its heart is the very same
simple box girder.

It's smaller and more crafted,

but it still relies on the same
hollow tube technology

pioneered by Stephenson
almost 170 years ago.

So how was it that a far off
corner of Wales

ended up with a bridge
that's so incredibly important,

not just to the history
of engineering

but to the history
of the modern world?

Well, the answer is twofold -
the Royal Navy and politics.

In 1845, Robert Stephenson,

son of the railway engineer
George Stephenson,

was employed to build
the Chester to Holyhead railway.

Part of the job was to connect
the island of Anglesey

to the Welsh mainland.

But it's what lay
to the west of Anglesey

that made the bridge
so important.

Beyond Anglesey is the Irish Sea
and then Ireland itself,

which back in the 1840s

was a turbulent part
of the British Empire.

The need for a fast connection

wasn't so that tourists could paddle
on the beaches of Anglesey.

It was to speed up
the vital strategic route

between London and Dublin,

which prior to the Britannia
rail bridge

had to stick to the slow routes via
Thomas Telford's suspension bridge.

But with the Industrial Revolution
taking hold,

faster railways were expanding across
the width and breadth of the UK.

But to reach the port at Holyhead,

they needed to cross
the dreaded Menai Strait.

Possibly the hardest part of the
entire 260-mile route to construct

was the bridge over this
treacherous stretch of water.

The obvious solution
would be to build a bridge

with two big arches -

one arch from the mainland

to the rocks
in the middle of the strait,

then a second arch over to Anglesey.

Stephenson himself came up with
a design to do just that.

But there was a problem -
the Royal Navy.

Back in the 1840s,
the Navy ruled the waves...

and they weren't going to have
a railway bridge

stopping them from ruling
the Menai Strait.

They demanded that any bridge
left two clear channels,

each over 400 feet wide and
a whopping 100 feet high

to allow tall sailing ships
to pass through unhindered.

You might think that Stephenson

could have simply copied
Telford's suspension bridge,

which lies about a mile to the east

and built almost a quarter
of a century before.

But that's a road bridge.
This needed to be a rail bridge.

Suspension bridges and trains
simply do not mix.

The massive weight of the train
can cause it to flex and sway so much

that it becomes a real danger
the train itself could derail.

So the suspension bridge was out.

The only other option

was to rely on the oldest type
of bridge in the book -

the simple beam bridge.

It doesn't get much simpler, really.

Two supports and a beam
across the top.

As a solution, it would keep
the Royal Navy happy because

it'd be the same height
above the water

right the way across its length.

But it has a fairly major drawback.
It's not very strong.

I'll show you what I mean.

If I stand roughly
in the middle here...

Ooh!

It just about takes my weight,

but only just.

You can see how much that's bending.

If I add another plank,
let's see what happens now.

There we go. Instantly much stronger.

But with each plank I put on,
it gets heavier.

And that's the problem.

My bridge here is
a couple of metres in length

and I'm adding about
80 kilograms on top.

And you can see the amount of wood
we need to make it strong.

Scale that up to what
Stephenson had planned,

beams to span over 450 metres
in length,

taking weights of hundreds
of tonnes at a time.

The sheer volume, and thus weight
of material required,

just made it a nonstarter.

The solution he came up with
wasn't just clever,

it would change the world.

And it was a solution
borrowed from nature.

At 460 metres long and
around 40 metres high,

nowadays a bridge
like the Britannia here

is nothing special really,

but around 170 years ago

it pushed engineering to
its absolute limits.

Back then, this great span

wasn't supported by
these huge arches we see today,

because the Navy had demanded
nothing should obstruct

the masts of their tall ships.

Instead, the entire bridge was
to be formed from great beams

which ran as a straight line
right across the Menai Strait.

As a concept, it sounds simple,

but the entire span of the bridge
would need to be 460 metres long,

and it would need to support trains
weighing hundreds of tonnes.

No-one had done anything
like this before.

Luckily, the solution to the problem
was right in front of them.

They just needed to know
where to look.

Now if I cut open
the stem of this plant,

you can see it's actually hollow
through the middle.

And it's that hole
all the way through

that gives the plant
its strength and rigidity.

And it's this clever trick of nature
that the Britannia Bridge exploited.

This is a solid aluminium rod.

This is aluminium,
it's exactly the same length,

but it's a hollowed out tube.

Now, they both contain
the exact same amount of material,

they weigh exactly the same,

so you might expect
they'd have the same strength.

But if I add on equal weights
in the middle,

let's see what happens.

Look at that.

Look at that bend
under the weight of that

almost-full bucket of water.

Right, watch this.

I'll now add on
exactly the same weight to the tube.

Something quite remarkable happens.

The tube hardly bends at all
compared to the solid rod.

And it was this phenomenon that was
the key to designing the bridge.

Rather than a simple solid beam,

the whole bridge would become
a massive tube.

Three towers would support
two 140 metre-long tubes

40 metres in the air,
each weighing 1,500 tonnes.

Two smaller spans of 70 metres

would then sit between
the outside towers

and the abutments on the banks.

When completed, the tube would be
large enough for trains

to run inside them,
across the entire 460 metre span.

Whatever that tube was made from,
it had to be very, very strong.

Today, we take metal as
a construction material for granted,

but in Stephenson's day
it was still something of a novelty.

This is the famous Iron Bridge
near Telford.

Built in 1777, it was the first
really large construction

made from cast iron.

In many ways, this bridge kicked off
the Industrial Revolution.

Beforehand, cast iron was mainly used
for small things, like pots and pans

and knives and hinges,
but this bridge changed that.

Suddenly it announced to the world

that cast iron was
the building material of the future.

Compared to wood or stone,

you get a lot more strength
per pound of weight,

but iron's main advantage
over its traditional rivals

was that you could cast it
into any shape you like.

It really was revolutionary.

But as strong as it is,
it does have a fundamental weakness.

It's actually extremely brittle.

Just watch what happens
when I give this bar here

even a mild tap with the hammer.

Look at that.

That's gone right through.

I can demonstrate what happens
using this twig.

Now, if I bend it down in the middle,

the bottom surface is being pulled,
it's being stretched.

It's what's called
coming under tension.

And it stretches and stretches
until eventually it cracks

and then breaks all the way through.

Here we go.

And that's exactly what happens
on the cast iron as well.

This deadly characteristic

was to result in the deaths
of five people,

and almost stopped
the Britannia Bridge in its tracks.

On the 24th of May, 1847,

a year after construction
had started on the Britannia,

the bridge over the River Dee,
another Stephenson design, collapsed,

causing a train to derail
and crash into the water below.

The accident almost cost
Stephenson his career

when he was hauled before the court
on a negligence charge.

He was eventually cleared,
as the collapse was blamed

on the insufficient strength
of the girders, not his design.

But the disaster made people realise
that cast iron

wasn't the wonder material
they'd thought.

But there is a way of stopping
cast iron from shattering,

and that's to hit it hard -
turning cast iron into wrought iron.

Traditional blacksmiths
Duncan and Jack

have set me up with a furnace,

a hammer, an anvil,
and a white-hot piece of cast iron -

everything I need to show
how wrought iron was made.

- Cor, look at that. That's a beaut.
- Give it a brush.

Heating cast iron,
then hitting and rolling it,

realigns the internal structure
of the metal,

making something that's rigid
and brittle more flexible

yet crucially without
reducing its strength.

It also helps remove impurities
like carbon and sulphur

that weaken its structure.

So, when you see a blacksmith
hammering away

on the anvil here in the workshop,

it's not just about
shaping the material.

It's giving it strength,
adding structure.

At the end of this
incredibly intensive process,

you end up with a piece of iron
with very different properties.

Now, this is a piece of wrought iron.

It's been through that hammering
and rolling process.

It's got virtually no carbon in it
and it's lost that gritty,

crystalline structure
that cast iron has.

In fact,
it's almost got a grain to it.

It's got a lot more structure,
and, as such,

it behaves very differently
to its cousin, cast iron.

Let's give it the same test here
with the hammer.

Yeah, that was very different.

The sound's different,
the feel's different in the hammer.

Now I'm really giving that
some wellie,

and I've put a bit of a kink in it.

I mean, if I really want to go for
it, I can pop it in the vice here.

Let's see what we can do here.

Alright, if I really try
and bend this...

let's see if I can
actually break it.

It's bending.

You can see I'm putting
a lot of effort into that.

This behaves extremely differently
to cast iron.

Of course,
when you're building a bridge,

the sheer volume of wrought iron
needed to be vast.

But, thankfully,
this was the Industrial Revolution,

and there was access
to massive steam hammers

and rolling mills to work the iron,

making it possible for the first time
to use wrought iron on a large scale.

But there was an even bigger problem.

Up until now, the longest wrought
iron span was under 10 metres,

more than 14 times shorter
than the 140 metres.

Stephenson was proposing.

Stephenson was in unchartered waters,

using a new technique
and a type of iron

never used before on this scale,

so to help him he brought in
two of the unsung heroes

of Victorian engineering -

a move that would result
in a bitter feud.

The first was William Fairbairn.

Iron was Fairbairn's forte.

His background was in shipbuilding,

and he had a works on this site here
in Millwall

near the River Thames in London.

If anyone could find out the best way

to make gigantic tubes
out of wrought iron, it was him.

Fairbairn stood out from his peers

because he was one of
the first engineers

to actually try and understand
and analyse why structures failed,

which, believe it or not,
was unheard of at the time.

The second member
of the Britannia team

was a mathematician
by the name of Eaton Hodgkinson.

Together, their task
was to experiment

with different designs of tubes

until they discovered ones
strong enough to span the strait.

I say together,

but Stephenson was actually
away a lot,

doing other gigantic projects
across Europe.

Still, the other two got stuck in.

Taking their inspiration from nature,

the team started with
cylindrical and elliptical tubes,

building lengths almost 10 metres
long and loading them with weights

until they broke.

The results
were always disappointing.

Try as they might, their oval beams
were never going to span the straits.

But then they switched to oblongs,

which is when Fairbairn had the idea
that would change the world.

And this is it.

Rather than just one big tube,
and it is enormous,

Fairbairn suggesting
using multiple cells.

These smaller tubes

across the bottom and the top

sandwiching the main central tube,

and the effects of this relatively
small change were incredible.

Suddenly they were experimenting

with hollow tubular beams
20 metres in length

that could support around
80 tonnes in weight.

It was a giant leap forward,

but there's a big difference
between a 20-metre prototype

and a 460-metre bridge.

This is just a small piece
of the full-size beam

they ended up making.

You can just imagine it stretching
right out across the Menai Strait.

It was revolutionary.

Of course,
modern bridges look nothing like this

great lump of iron,

but it was Fairbairn's
simple innovation,

those tubes along the bottom
and on the top -

a key to so many bridges
around the world.

And it would prove to be
even more important than that.

In the 1840s,

the longest ships in the world
were only around 80 metres.

Any longer and they tended to snap
in the middle in heavy seas.

But the box girder helped
change all that.

It gave us the ability to construct
a rigid beam hundreds of metres long,

and it's that that's allowed us
to build the huge ships

that have shrunk the world.

And by huge, I mean HUGE.

Today, thousands of massive cargo
ships and oil tankers

navigate the world's oceans.

Some are as long as
the Britannia Bridge itself.

And it was only possible
because of the humble box girder,

designed to cross a small strait
in North Wales.

But coming up with the means
to cross the Menai Strait

was only part of the solution.

Designing a beam that could span
these great distances was one thing.

Building it across this deadly
stretch of water would be far harder,

and in the end, it would result

in one of the biggest bust-ups
in engineering history,

denying William Fairbairn
the limelight he so deserved.

Back in 1849,
Stephenson's Britannia Bridge

was one of the biggest
civil engineering projects

in the world.

Huge stone towers holding up

a 460-metre-long hollow beam
of wrought iron

across one of the most dangerous
stretches of water

in the British Isles.

One of the truly brilliant features
of the Britannia Bridge

was that Stephenson and
his colleagues found a way

of making that beam incredibly strong
but also incredibly light.

But that weight-saving concept
didn't end there.

The central towers and
huge stone structures at each end

may look solid,
but in fact they're hollow.

Are you ready, Rob?
Here we go. Yeah.

And that means you can go inside.

These magnificent structures
are normally closed to the public,

but I've been given the chance
to join Network Rail,

owners of the bridge,

as they give the 176-year-old towers
a health check.

Gary, I'm still getting over how
surprising, magnificent...

Kind of lost for words
just how amazing it is in here.

Yeah, Rob,
this is Anglesey railway abutment.

It's the biggest of the two
aptly named cathedral abutments.

As you can see, the sheer size of it.
It's enormous.

I did not expect, when I walked in,
that this was what was awaiting me.

It's huge. 33 metres high,

55 metres long from abutment face
to back wall,

and around 20 metres wide.

This cathedral abutment is
held up by three enormous arches,

which in turn have 14 smaller arches
sitting on top of them

holding up the rail track.

It's like a giant wedding cake,

with each tier
supporting the one above.

Essentially, this big space
is saving on material.

You can imagine
the volume of material

that'd be needed
to fill this sort of space.

Tie bars provide lateral support
to the external walls,

stopping the external walls
from spreading.

It travels from one wing wall
to the other and keeps them in sit...

It just amazes me that
after all this time,

almost 170 years,

all of this is still doing its job,
taking the weight of the trains,

and now the cars as well.

It's amazing.

The foundations for these towers
were laid in 1846,

and it took Stephenson three years
to finish them.

But by 1849, the towers were ready

to bear the weight of
the massive box girders -

thousands of wrought iron plates

held together by over
two million rivets.

But no-one had ever made
a bridge like it before -

and the risks were phenomenal.

The legendary engineer
Isambard Kingdom Brunel,

a rival and friend of Stephenson,

is said to have told him that,
"If your bridge succeeds,"

"then mine have all been
magnificent failures."

Which is one of the reasons why
Stephenson decided on a rehearsal

and built this.

The Conwy tubular bridge,

about 20 miles down the line
from the Britannia Bridge,

which opened in 1849.

The crossing here is less than
half the span of the Menai

and not nearly as high,

but it was, in many ways,
a dry run for the Britannia Bridge.

Passengers travelling by train
will barely notice it,

little more remarkable than passing
through a rather short tunnel.

But from the outside,
you can appreciate its magnificence.

From underneath here,
along the length of the bridge,

you can see where those cells,
developed by Fairbairn, run,

giving the bridge its strength.

It's still taking the weight of
around 50 trains a day

almost 170 years
after this was built.

In many ways,
there's no better testament

to the box girder than this.

The massive girders
were constructed on the banks,

then the huge 400-foot structures
were floated on rafts downriver

to be jacked up
to their final resting place.

The idea of floating an
1,100-tonne beam along the river

and then lodging it exactly in place
between these two huge stone towers

seems bonkers
even by today's standards.

Against all the odds, it worked,

and the Conwy Bridge
was up and running.

But if Stephenson thought
that was hard,

it was nothing
compared to what faced him

when he tried to cross
the Menai Strait.

Unlike the relatively calm waters
at Conwy,

the currents in the Menai Strait
are much fiercer

because the strait isn't a river,
it's sea.

Twice a day, tidal currents sweep
through this narrow strait

in both directions,

creating dangerous and
unpredictable conditions.

Admiral Horatio Nelson described this

as one of the most treacherous
stretches of sea in the world.

Not only is it more dangerous,
it's also much wider than at Conwy,

so Stephenson decided
to cross it in two sections,

each one 140 metres long.

Early on a June evening in 1849,

they started to float
the first tube down the strait

on pontoons controlled
by ropes from the bank.

It was launched from the riverbank
right behind me here,

and at 140 metres in length,

it was longer than any ship that
had been built at the time.

About half as wide as
the Menai Strait itself,

it would span the gap
between the Anglesey side

and the central tower here.

Just like the tubes at Conwy,

these monsters would be
floated into position,

but the risks were much higher.

They would only be able
to launch the tubes at high tide,

but this would only give them
an hour of relative calm

before the vicious currents
would sweep through the channel.

If the tubes were not secured
by then, disaster would strike.

Thousands of people turned out
to witness the event of a lifetime.

All was going well until
one of the ropes got tangled up.

One of the anchor points on shore
got ripped clean out of the ground.

In a move that would put

a modern health and safety officer
into a cold sweat,

the spectators were
called upon to help,

hauling on ropes
to try and save the tube.

Incredibly, it worked,

and the first tube
drifted into position

at the base of the towers.

And then came the next challenge -

lifting the 1,600-tonne tube
40 metres up

to its final resting place
near the top of the towers.

So how did they do it?

Well, the secret is hidden

in the remaining sections
of the bridge.

It's just that very few people
get the chance to see it,

as you need to climb below
the modern railway track.

Stephenson decided
to use hydraulic jacks,

designed and built
into the towers themselves,

to lift the huge tubes into place.

The jack, a simple cylinder
with a piston inside,

was connected by chains
to the box girder below.

A steam engine would inject water

at thousands of pounds
per square inch into the jack.

That high-pressure water
pushed the piston upwards,

the chains raising the beam
about two metres at a time.

Then the tubes would be secured,
the chains shortened,

and the whole process
would start again

for the next couple of metres' lift.

These vast, vertical grooves
in the towers here,

one here and one on the other side,

they run right down to the water -
the whole height of the tower.

They're what guided the ends
of the tubes

as they were slowly lifted up.

The pressure needed to lift
the 1,500-tonne tubes

would've been immense,
even by today's standards.

In many ways, it was like
a bomb waiting to explode.

And on the 17th of August, 1849,
that's exactly what happened.

The very first beam
was only seven metres up the column

when, bang,
the entire jack exploded.

And to show you
just how big a bang that was,

this is the remains
of that very jack.

The centre,
that would be hollowed out.

That's where the piston would be
driven up and down by the hydraulics.

But it's the
thickness of the walls

of the cylinder that gets me.

You can see
this is where it's broken,

this is where it's failed,

but that thickness,
it's about a foot there.

It just goes to show
the phenomenal pressures involved

to break this.

One man died in the accident,

and the damage caused brought
the entire bridge build to a halt.

The setback meant
it took another eight weeks

to get the tube positioned
at full height,

but it was soon joined by
another tube on the other side,

and the Menai Strait was spanned.

Stephenson himself
hammered in the final rivet,

and his revolutionary plan
for a railway tunnel in the sky

had worked.

And for the next 120 years,
trains would thunder across

Robert Stephenson's Britannia Bridge
day and night.

But the success was also to lead
to a very public and bitter fight -

one that would take almost
170 years to resolve.

The first clue to the dispute
can be found here

at the Institution of Civil Engineers
in London...

in this great painting.

It's a fictional scene.

You've got Britannia Bridge
in the background there,

Stephenson right in the middle

holding court,

surrounded by his contemporaries.

And even his good friend Brunel

makes an appearance,

who had absolutely nothing
to do with the bridge.

But, astonishingly, there's

absolutely no sign of Fairbairn.

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

And there's a reason for his absence.

Fairbairn and Stephenson
fell out publicly

over ownership of the box girder.

It was a fight that even today

is considered one of the biggest
bust-ups in engineering history.

Hidden within the institution's
own library

are a series of correspondence
between the two men

which clearly sets out
the disagreement.

And this is a real privilege here.

These are the original letters,
Fairbairn's letters to Stephenson.

And this is engineering history
right here.

This letter here is the first time

that he sets out the results
of his tests,

and where he suggests the idea
of the cellular tubes

along the top and on the bottom
as his idea,

his solution for
the Britannia Bridge.

So here we go. Written in Millwall,
September the 20th, 1845.

"It is more than probable that
the bridge in its full size"

"may take something of
the following sectional shape."

And there it is.

There is his cellular idea,

with those smaller tubes
across the top and the bottom.

Now, in it, he refers to Hodgkinson,
the mathematician he worked with,

but there's absolutely no doubt
Fairbairn was instrumental

to this idea.

But three years later on,
on the 17th of May, 1848,

Robert Stephenson made a speech
that seemed to make plain

that the idea was his

and that Fairbairn
had played little part in it.

And this is a copy
of Stephenson's speech here.

Stephenson's words.

"It is now upwards of six years
since I entertained the idea"

"of constructing bridges with wrought
iron plates riveted together."

And he goes on.

"I had satisfied myself that
the thing was practicable,"

"and I stood by it."

"In order most thoroughly
to test experimentally"

"the theory I had formed..."

It's all beautiful
Victorian language.

"It was then that I called in
the aid of two gentlemen -"

"eminent, both of them,
in their profession -."

"Mr Fairbairn and Mr Hodgkinson."

"They were well qualified
to aid me in my research."

For Fairbairn, the amount of "me"
and "my" and "I" in that speech

must have been just too much.

Fairbairn formally resigned,

and spent the next year writing
a book to set the record straight.

Straightaway, on page one,

he sets out his intention,

"To establish my claim
to a considerable portion

"of the merit of the construction
of the Conwy and Britannia bridges."

"The various public statements
which were made at different times"

"by different individuals which
either entirely passed over"

"or concealed the real nature of
the services I had rendered."

The whole thing was a right old
ding-dong between the two of them.

Not necessarily what you'd expect
from two well-mannered,

proper Victorian gentlemen.

Almost 200 years later,

many in
the Institution of Civil Engineers

have come to realise
Fairbairn's true importance.

In this, the Stephenson Room,

Fairbairn's portrait
now hangs opposite the scene

he should be portrayed in.

Now I like to think this helps
set the record straight.

Equal status for them both.

We'll never know why Stephenson felt
so sure he should take major credit

for the box girder
and the cells across the top

that gave the Britannia Bridge
its great strength,

but, in my view,

Fairbairn deserves his recognition.

He ought to be remembered amongst
the great Victorian engineers

alongside the likes of Brunel
and Stephenson.

For over a hundred years,
trains hurtled over their bridge,

keeping the vital link to Ireland
open day and night.

But on the 23rd of May, 1970,

something happened that
no-one could've imagined.

The bridge caught fire.

Right from the very start,
Stephenson's Britannia Bridge

was more than just
another bridge crossing.

It was a vital link
between London and Dublin.

It towered over the Menai Strait,

connecting the rest of the UK
to the strategic port at Holyhead

for 120 years.

But on the 23rd of May, 1970,
that link was severed,

putting the whole port out of action.

It was 9:43 in the evening when
the fire brigade received reports

that Stephenson's great bridge
was ablaze.

The fire was destroying one of
the most significant innovations

in engineering in over 200 years.

But how could a wrought iron bridge
catch fire?

The answer is because of a mistake
made by this man, Edwin Clark.

He was one of Stephenson's
key engineers on the project

and was left in charge for
the final few weeks of construction,

and it was his bright idea
to add a roof.

He added an arched timber roof
covered in a tarred hessian,

which he hoped would protect
the iron from the weather.

My guess is it was some kind of
early roofing felt,

but it perhaps wasn't
the cleverest of ideas,

because, unlike iron,
this stuff burns really well.

On that fateful night,

a group of local lads
entered the tube.

Without any torches
they lit some paper,

and the burning embers
dropped to the floor.

It's not exactly clear how,

but these embers caused
Clark's roof to catch fire,

and once the highly flammable mix
of tar and wood was ablaze...

the fate of the bridge was sealed.

Two of the firemen who were on duty
that night still live in the area,

and it was a night
they'll never forget.

When you first arrived there and
both saw what was in front of you,

what were your reactions?

What did you think? "Wow."

There was no saving the bridge.

Really? You could tell straightaway?

It was like fighting a chimney fire,
if you like, on its side.

If it was building on fire,

we could have tackled it from
four corners and perhaps from above,

but because of the location
of the bridge,

you could only tackle it
from this end of the tunnel

to the Anglesey side.

In-between, it just burnt.

But that fire was spreading
away from you? Yes.

There was no saving the bridge
at all. It was just an inferno.

Could you feel how hot it was?

Could you kind of sense
how hot it was?

Very, very.
The radiated heat was terrible.

When you projected water
into the tube

it turned into steam,
so it didn't do much work.

Wow.

There was no way at all
you'd go into the tunnel.

At all.
You'd have been roasted alive.

Also there on that night
were two local cameramen

who rushed to the scene
to cover the fire.

So, you were both there
with your cameras?

Yes, indeed. Yes, indeed. Yeah.

So, filmed it and took photographs.

There's the pictures
of the actual fire.

You can see the amount of material
that's falling off it. It was incredible.

So, you were underneath the bridge
then, were you?

You were down by the water.
Yeah, as close as practical.

Very, very noisy. Was it?
Incredibly noisy.

Absolutely, yeah.

Bits flying down.
What kind of noise?

Just crackling and burning.

This is debris just dropping down.
That's falling off it.

That's the debris that's on fire.
Absolutely, yeah.

And this was the most
spectacular fire.

Debris was falling off
in great big chunks,

and where it landed in the strait,
of course, it was still alight.

The next morning,
the bridge was still smouldering

and the damage was obvious.

It burnt well into Sunday,
about four o'clock, didn't it?

Yes. It burnt itself out.

And all you could do was...
Just keep damping down.

It was a token gesture, wasn't it?
Yes, that's all.

Stephenson's revolutionary tubes
were sagging by over half a metre,

suggesting temperatures
inside the tube

must have exceeded
1,000 degrees Celsius,

and they were now resting
so precariously in the towers,

it was feared
they could fall at any moment.

The historic box girders
were utterly destroyed.

The destruction of the bridge

was without doubt an historical
engineering tragedy,

but with it gone, a more immediate
nightmare was unfolding -

one that threatened the livelihood
of the whole island of Anglesey.

Thanks to the success of the railway,

an important and prosperous
container port

was operating at Holyhead.

A new power station
and aluminium smelter

was under construction.

The island was booming.

But without this bridge,

Anglesey would become
an economic disaster zone.

A replacement bridge had
to be designed - and quickly.

In a matter of weeks,

a plan was agreed and was
rushed into construction.

And it's that bridge that
still stands here today.

The new bridge is not spectacular
or revolutionary,

but practical and efficient.

It carries both trains and cars,
split on two levels.

It uses the same towers built by
Stephenson almost 170 years ago,

but now its weight's taken by
its two great arches.

Ironically, a more traditional way
of crossing a river,

but as there are no tall
naval ships around any more,

it was the simplest option.

The new bridge was commissioned,

designed and opened
in less than two years.

As a rushed job,
it doesn't look too bad,

and despite the arches,

it still bears
considerable resemblance

to Stephenson's masterpiece.

As an engineer,
I feel sad that the key component

of the Britannia Bridge -
the tube that changed the world -

was sent to the scrap heap
in the 1970s.

And for me it's important
to remember its inventors,

Robert Stephenson,

and William Fairbairn - one of
the forgotten greats of engineering.

Captions by Ericsson Access Services
SBS Australia 2017