Original subtitles

The real accumulator had 120 tonnes of pig iron inside pressing down.

To prepare the accumulators for action,

water was pumped into a cylinder under the floor here

at 750 pounds per square inch -

13 times the pressure of a typical household water supply.

I have a basic model of this extraordinary machine

to explain how it works.

Now, inside the cylinder was a huge piston and, so,

the reason you needed such high water pressure

being pumped into the bottom of the cylinder

was because that piston was being weighed down.

Now, I'm using a can of beans.

And there are three others hidden inside the piers.

So now I've got this mass being held at height.

This would have been pumped right to the top of this tower here,

a huge amount of potential energy.

Whenever they wanted to do a bridge lift,

all they needed to do was open the valve at the bottom of the cylinder

and let the water out.

As the 100-tonne weight descended,

that high pressure was shot with enormous force

into driving engines - essentially, huge gearboxes.

Those gears turned a shaft that was connected to the back

Four of them are buried inside the bridge's massive supports -

they had to be ready to lift the bridge.

It couldn't get stuck 'cause if you imagine it got stuck

when the bridge was up, it would cause traffic chaos in London,

nobody would be able to get anywhere.

If it got stuck down, then the boats wouldn't be able to get through.

Although the 360 horsepower steam engines

could lift the bridge on their own,

that wasn't their main job.

They were designed to pump cold water

into Victorian energy storage devices called accumulators.

It's the accumulators that really powered the bridge.

of the moving part of the bridge, the bascules,

the piers.

Normally, the piers are off-limits to the public,

but we've been allowed to take a look.

I'm now deep inside the south pier

and the first surprise is it's hollow.

From the outside, you'd think it was made of solid stone,

but that's not the case at all.

And once you come down in here, you can see why.

This is one of the main accumulators.

It's a giant.

is that from on top of the bridge, you can't even see it.

It's all about to happen.

Here we go.

I'm now standing as close as a human being is allowed to be

as this gigantic Victorian machine comes to life.

Look at it! It's right there!

It's not fast, it's majestic.

(CHUCKLES WITH DELIGHT)

Here we go. Job done.

Beautiful. Beautiful.

One of the most impressive things

about this fast and complex arrangement

literally.

Almost everything was tucked away below the main road deck.

It's another one of the remarkable things about Tower Bridge -

it would work perfectly well without its towers.

The main reason the towers were built, of course,

is to hold up the high-level walkways.

But the truth is for most of the bridge's life,

those walkways were never even used.

Originally, the river authorities wanted the bridge to be lifted

for two hours every day at high tide,

so the walkways were added so pedestrians could keep crossing

But these leaves weigh 1,200 tonnes each.

raising them in 90 seconds flat.

This is the bascule chamber.

And above me is the bascule.

It's the back end of the bascule and what we can see,

the huge white area, that's the counterweight.

So when they want to lift the bridge,

the front end of the bascule,

the road section goes up

and the back end swings down into this huge, cavernous void.

Each side of the bascule is called a leaf.

so as soon as a boat needed to come,

The cast-iron counterweights alone weigh 450.

I need to leave the bascule chamber now,

because the bridge is about to lift and, for obvious reasons,

the staff don't want anyone in here

when that thing above my head comes swinging down, so...I'm out.

Although I can't be inside the chamber itself,

I have been allowed to stand just next door in the service tunnel.

(ALARM WAILS)

I'm about to witness something few people ever get to see.

The underside of Tower Bridge swinging into action -

The early years of the Industrial Revolution were much the same.

that really hold the bridge up.

In these remarkable photos taken in 1892

while the bridge was under construction,

the steel skeleton can plainly be seen.

Later pictures show the familiar stone facing being attached,

but why bother covering up the bridge's true nature?

Partly, the stone walls act as a form of weatherproofing,

but there's another reason.

One look out over London with its cutting-edge architecture,

tall glass tower blocks,

tells you that modernity is very much in fashion.

concealing the 11,000 tonnes of steel

People liked seeing exposed metal structures.

It felt modern.

But by the 1880s, there was a backlash against modernity.

Instead, leading lights of the day

championed a style called neo-Gothic.

They wanted to recreate England as a kind of medieval fairytale.

Brutal steel framework wasn't part of that story.

It's almost like the bridge has been camouflaged,

it's been deliberately designed to look like a medieval castle,

just so it doesn't ruin the view

And many people assume that's where it gets its name.

But the handsome stone we see actually hides a strange secret -

an engineering trick that most people know nothing about.

Whether it's throngs of tourists taking selfies

or one of countless postcards and souvenirs on sale nearby,

images of Tower Bridge are everywhere.

It's the most famous bridge in the world.

But hidden inside this British icon,

there's a labyrinth of contradictions and unexpected surprises.

The towers are undoubtedly the bridge's most remarkable feature.

They are what make Tower Bridge so famous.

of the real medieval castle right next door.

But it's actually named after its much older neighbour,

the Tower of London.

The bridge's name isn't the only misconception about it.

In fact, the handsome stone bridge we see from the outside

isn't really a bridge at all.

It's only when you step inside the towers

that the real bridge reveals itself.

Because Tower Bridge isn't made of stone.

It's made of steel.

The famous stone walls are just a facade,

This is beautiful machinery.

These boilers were used to create steam

that powered the rest of the machinery.

This is the start of a system

that was a marvel of Victorian ingenuity.

When these engines were in use, men worked here 24 hours a day,

seven days a week, 52 weeks a year.

Today, it's a museum.

Much of the grimy machinery has been cleaned up

and lovingly restored.

And welcome hosts like Katie Williams

are on hand to explain it all to visitors.

to the bridge in the old engine rooms.

I can't get enough of this stuff.

This is the last stage of the bridge lifting, isn't it?

Yeah, the very final stage of lifting the bridge.

How long would it take to actually get the bridge to fully lift?

So it would take around 90 seconds to lift the bascules.

The entire time, though, using the steam system, it never failed,

from 1894 until 1976.

That's brilliant!

I like that.

The river traffic always has priority,

and when the bridge opened, everyone gasped.

In 1894, after six years of construction,

this colossal Victorian fantasy was complete.

On top of the steel, it took nearly 37,000 tonnes of concrete,

30,000 tonnes of masonry

and more than 27,000 tonnes of brickwork to finish it off.

On June 30 of that year,

a grand ceremony was held to mark the bridge's opening.

The Prince of Wales, the future king Edward VII,

was given the honour of raising Tower Bridge for the first time.

The Prince of Wales was standing right about here

while it was open.

No-one had ever seen anything quite like it before.

People started calling it the Wonder Bridge.

It's a name that's richly deserved.

Ever since that day,

people from around the world have been awestruck

by the sight of Tower Bridge

raising its 61-metre-long central span.

But most of them have no idea

just how clever the lifting mechanism really is.

I'm now underneath the South approach road

The lifting process starts with a short announcement

The problem is, her tallest masts are 15 metres high.

Whereas the clearance under the bridge is only 10 metres.

That means Tower Bridge needs to go up

and I've been given special permission to lift it,

under the watchful eye of bridge technical officer Sean Naidoo.

When I - and in this case, you - are opening the bridge,

you have responsibility of the vessel,

the people on the road,

members of public, members of staff, and anyone nearby, so...

You've now just made me very...

Should go alright! You've now just made me very nervous.

And she wants to leave the pool of London and head downstream.

to clear the bascules.

Stand-by, bridge crew. Stopping traffic.

Is it happening? There we go. (ALARM WAILS) OK.

Once the bridge has been emptied of people and vehicles,

I can take control of a British engineering landmark.

Now you can do the nose bolts, which is next to...

This one here? Yeah.

Hand on the lever. That's open.

OK, yeah. Right. And pull it towards you a little bit.

Just to get it moving at slow speed. Keep it there for a few seconds.

It's not as exciting as the steam engine,

states river traffic could NEVER be obstructed,

and that's still the law of the land today.

So, the city went for another option -

drastically cutting costs through modernisation.

The grand old steam system was finally retired in 1976

and this was installed in its place.

It's an electrically-powered hydraulic engine.

A huge pump that forces hydraulic fluid into the drive system.

This is the set-up that drives the bridge

here on the south-east side

and there are three identical systems on the other corners of the bridge.

Right, now all the way.

but it's way more efficient.

That said, from this yellow piece onwards are the original parts.

The new electrohydraulic system

meant that the team of 82 people

that used to keep the bridge running was reduced to just 15.

And lifting the bridge takes just one.

There's a sailing barge called Gladys and she's waiting upriver,

somewhere just over there, can't quite see her here.

Now, she's typical of the ships

that used to ply the river day in, day out.

the city took another step to breathe new life into the bridge.

is its patriotic red, white and blue colour scheme.

But it hasn't always been like that.

For most of its history, this bridge was painted...brown.

In 1977, that became a bit of a problem.

The bridge was due to feature prominently

in the Queen's Silver Jubilee celebrations.

Only the existing paint scheme wasn't very jubilant.

The bridge was repainted with a much more festive red, white and blue.

It was such a hit with the public,

the city decided to keep it and it's been with us ever since.

And in 1982,

Probably one of the most distinctive things about this bridge

The old walkways, which had been out of use for more than 70 years,

were reopened as a tourist attraction.

Today, it's a big hit with more than half a million visitors every year.

It's hard to conceive of London without Tower Bridge.

But now I know the story of how it almost never came into being

and how close London came to losing it through the war

and through economic decline.

It makes me think how lucky we are to have it.

It really is the Wonder Bridge.

Captions by Ericsson Access Services (c) SBS Australia 2017

There he is. Oh, lovely.

That was brilliant. Here we go. Up you go.

That's it. (CHUCKLES)

Oh, yeah. This is a dream come true.

It's a lifelong dream come true.

Look at it! That is amazing.

Just the amount of steel,

the sheer weight that my hand on this lever is pulling up.

Gently come back to the middle position.

And give them a green light, which is next to your right hand.

This one here? That's it.

the Act of Parliament that authorised its construction

There you are. Congratulations, Rob.

That was brilliant. You've just lifted Tower Bridge.

Oh, thank you so much. How did I do? Did I do alright?

Oh, you did fine. Yeah?

Nothing's crashed into anything. Excellent.

Safety, I've still got a 100% record. Yeah. 100% record.

Excellent. Let's keep it that way.

While updated machinery gave Tower Bridge a new lease of life

on the inside,

the weathered exterior was looking increasingly drab and tired.

it had a very close call.

and the city that surrounded it.

In 1940, London was threatened with annihilation from the air.

The Blitz had arrived and target number one was London's docks.

The economic engine of the whole British Empire, Tower Bridge,

was right in the firing line.

Nazi pilots used the bridge as a navigational aid,

lining up their bombing runs with the towers as they headed up river.

During The Blitz,

bombs hit pretty much every building in the area

including extensive damage to the Tower of London, just feet away.

Somehow, the bridge wasn't hit, but on 16 January, 1941,

brought about a drastic change for the bridge,

A bomb narrowly missed,

but hit a tugboat called the Naja just alongside.

Sadly, two crewmen were killed.

Those two joined the more than 17,500 Londoners

that had died by May 1941.

But then, for a time, the skies above London were clear.

That suddenly changed on June 13, 1944,

when this East End railway bridge was hit with a terrifying new weapon.

That weapon was the V1 flying bomb.

This unmanned, unguided weapon was crude but effective.

For more than 70 years, the towers were little more

Only, that part of the plan never happened.

The bridge could be raised and lowered so quickly,

it wasn't necessary to keep it open for long stretches.

Tower Bridge lifting was such an incredible sight,

most people didn't bother traipsing all the way up here to get across.

They'd much rather wait and watch from down there.

It was way more interesting and much faster.

The walkways became little more than a hangout for prostitutes

and pickpockets and in 1910,

they were closed to the public, just 16 years after they'd opened.

The Nazis aimed it at a preset target and let it go.

than expensive scaffolding for hydraulic pipework.

But when World War II darkened London's skies,

those towers became something altogether more sinister.

This great British monument was transformed into a Nazi target.

From almost the day it opened in 1894,

the raising bascules of Tower Bridge

became a familiar sight to Londoners.

In its first year of operation, the bridge lifted 6,000 times.

A pace that hardly changed for the next half-century.

But the start of World War II

road traffic going across the bridge was becoming ever heavier

The driver, Albert Gunter, made it safely across

and his passengers suffered only minor injuries.

He was given a £10 bonus for his heroics.

The bridge had survived all this,

but its fate was nearly sealed by something much slower

and harder to see - economic decline.

By the early 1970s, the pool of London here,

once the heart of the busiest port in the world, was dying.

The advent of containerised shipping meant that most of the cargo

was now being unloaded at a new port, Tilbury, some 20 miles to the east.

At the same time, thanks to mass car ownership,

and the bus jumped over the gap between the bascules.

and lifting it became more and more of an inconvenience.

In order for the bridge to be lifted 24 hours a day,

the boilers needed to be fired, maintained,

and fed with coal around the clock.

But bridge lifts were becoming an increasingly rare occurrence.

The City of London finally decided

it was time to retire the old steam-driven system

and they seriously considered never opening the bridge again.

But even if the city had wanted to leave Tower Bridge permanently down,

they couldn't.

This time, the entire crew of six men died.

A timer then sent it into a dive after a prearranged flight time,

sending it plummeting to the ground, destroying whatever it hit.

There were around 10,000 V1s unleashed on London

and it's a little-known fact that they all have the same target.

Tower Bridge.

The weapon's guidance system was so primitive, though,

the bridge was hit just once

when a V1 bounced off one of the towers.

By a horrific twist of fate, the same tug that was hit in 1941,

the Naja, was hit again in the middle of a shift change.

with a mix of Cornish granite and Portland stone.

By some miracle, Tower Bridge made it through the war

virtually unscathed.

The post-war years saw several lucky escapes, too.

Like a number of planes flying between the towers.

But possibly one of the most extraordinary things

that ever happened on Tower Bridge

took place on 30 December, 1952.

That day, a number 78 bus was on its usual route across the bridge when,

without warning, it started to open.

A bridge worker had failed to stop the traffic

London was the busiest port in the world

there was nothing except miles

of open river all the way to the sea.

The frenzy of bridge building

was great for Londoners

living down this way in Lambeth, Chelsea, Putney or Hammersmith,

but for people over here, in Wapping, Bermondsey, Limehouse or Greenwich,

it was no help at all.

By 1875, more than one million people were living east of London Bridge

and they had no river crossing of their own.

There was one reason nobody wanted to build a bridge east,

in the East End - ships.

To the east downstream,

and many of the ships were sailing ships with tall masts.

A huge number of them were headed to the innermost part of the harbour.

The stretch of river downstream of London Bridge

called the Pool of London.

Often, they'd need to unload right here at Custom House,

so building a new bridge could help relieve the road traffic problems -

but only at the cost of blocking river traffic.

The port was London's biggest industry

and closing the river with a bridge would kill it dead.

But, ironically, the success of that industry

take an expensive riverboat

gives you a real sense of the hustle and bustle

and how busy this bridge would've been

in amongst all the shops and the houses.

This wasn't just a bridge, it was a small village.

It was lined with dozens of buildings

that had shops on the ground floor with houses above.

At the bridge's southern end was a defensive gateway,

topped with the severed heads of traitors on spikes.

For more than 1,500 years,

anyone wanting to cross the Thames had three choices -

you could fight your way through the chaos on Old London Bridge,

meant that more and more people were living and working

or make the round trip of more than 20 miles along to the next bridge

at Kingston upon Thames,

at that time a small village and far beyond the city.

It took centuries for London to get a second bridge,

Westminster Bridge, which opened in 1750.

In the decades that followed,

dozens of new bridges sprung up

across the river,

but every one of them was west,

upstream of London Bridge.

you've got the third type of bridge that opens to let ships through,

the people of the East End would finally have a bridge of their own.

And what a bridge it was!

At the time of its construction,

Tower Bridge was one of the most complex bridges ever designed.

For one thing, Tower Bridge wasn't really just a bridge, but three.

On the sides here leading from each bank to the towers,

it's a suspension bridge.

Then, there's a second style of bridge up above the first -

these high-level walkways.

They're a kind of box girder bridge.

Finally, right in the middle, and right beneath me here,

After decades of struggle,

the bascule bridge.

As a general rule, engineers like to keep things as simple as possible.

Tower Bridge is anything but.

That's all the more surprising

considering that many important people

never wanted it built in the first place.

For centuries, powerful interest groups

who oversaw shipping on the Thames

strongly opposed any kind of bridge in the East End.

There was simply too much money at stake.

The London Marathon,

around the docks of the East End

and they needed a bridge.

How could there be a river crossing for the East End

without blocking access for ships?

It was a simple question.

But one that would take decades to answer.

It was a problem even the greatest engineers of the day couldn't solve.

Until one obscure architect found a solution

in something as simple as a children's game.

Tower Bridge has been the centrepiece of countless national celebrations.

And all the people and animals and carts

royal jubilees,

and even the Olympics.

The bridge has become such a familiar part of the London cityscape,

it is easy to forget that it's not all that old.

It was a creation of the late Victorian era,

built to solve a particular late Victorian problem -

how to build a bridge in the heart of the world's largest city

without closing the world's busiest port.

In 1886, construction started here

on London's newest and easternmost bridge - Tower Bridge.

But today, sailing a full-sized cruise ship

But the Tower Bridge that everybody knows so well is not what it seems.

This familiar structure hides a world of secrets

and amazing stories from the tops of its towers,

to the depths of its foundations.

I'm going to explore it all and, really,

there's only one way to start my journey.

I'm heading to the very heart of the city to Tower Bridge,

but I'm not going by tube, I'm not going by bus,

I'm arriving on a ship.

100 years ago, arriving in London this way was nothing special.

6,000 ships passed under Tower Bridge every year.

has become an international symbol of Britain and its capital.

into the very core of the city is an extremely rare event.

Even the captain's excited.

There is some ports in the world

where you have to arrive with a vessel

and London is definitely one of those.

How many times have you sailed up the Thames and through Tower Bridge?

It will be my first time today. So, I'm the lucky one.

I know what means this bridge for the British people

and this is a bridge that is famous in the world, so...

It's our Eiffel Tower, if you like.

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

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.

But you just can't sail under the Eiffel Tower.

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.

In the heart of London, there is a unique monument - Tower Bridge.

The most famous bridge in the world and a true British icon.

Completed in 1894, almost 65 metres high,

and spanning 268 metres across the River Thames,

London's only opening bridge

of St Magnus-the-Martyr.

forgettable structure.

So how come this one is so extraordinary?

To understand that, we have to go back to a time when it didn't exist,

a time when London had just one bridge - London Bridge.

London Bridge has existed since at least Roman times,

but it's been through a number of different incarnations.

The London Bridge that we see today was completed in 1973.

It replaced a 19th-century version completed in 1831.

Before the 19th century London Bridge,

there was Old London Bridge,

and it started right here in the church yard

Often with an approach like that, you end up with a bland,

For more than 600 years, it stretched out from this point

across to Southwark on the South Bank.

And it was an incredible sight.

Inside the church,

there's something that will give me an idea

of what Old London Bridge was like.

And this is it.

One of the parishioners here built this model of Old London Bridge.

And it's absolutely incredible!

The detail is phenomenal.

called the Wonder Bridge.

That's true, that's true.

(BRIDGE ALARM WAILS)

Fantastic.

London is a huge metropolis.

People are busy, they've got stuff to do.

But when Tower Bridge opens, they stop and stare.

What a huge, huge privilege. (CHEERING AND WHISTLING)

(HORN BLARES)

Welcome to London.

This is the story of an object that Victorian Londoners

This wealthy coalition of ship-owners, merchants,

It's hard to imagine London without Tower Bridge,

but getting this bridge built was a monumental struggle.

In fact, it almost never happened.

It's a tale worthy of Dickens -

a clash between a wealthy few and the poor masses of the East End.

The conflict was only resolved

when a group of city leaders engineered a happy ending.

Everything about Tower Bridge, its shape, the materials used,

even the fact that it opens in the middle,

is the result of a tangled set of compromises.

Tower Bridge was going to cost a fortune.

while also making sure pedestrians

would never have to wait while the bridge was open.

In October 1884,

London's Special Bridge or Subway Committee

chose this revised plan as the winning design.

Their cause was no doubt helped

by the fact that Sir Horace was a member of the committee.

He voted for himself, naturally.

Jones and Barry had a plan at last that, on paper at least, would work.

But it was complicated.

All the many changes and additions meant one thing above all else -

giving ships more room to manoeuvre

The budget was £1,187,000.

And would cost well over 100 times that today.

Fortunately, for the City of London, who had to pay for this new bridge,

money was no object.

But even more fortunately for the British taxpayers,

it wouldn't cost them a single penny.

That's because the entire cost of building Tower Bridge

came from medieval Londoners.

In the year 1282, 700 years before Tower Bridge,

the city of London started to collect revenue from Londoners

Once again, the port authority stepped in with objections

That helps traffic on the river move smoothly,

while keeping delays on the road to a minimum.

Bascule bridges weren't a new idea.

The thing that was different

about Sir Horace Jones' design was the scale of it.

Tower Bridge would be the biggest bascule bridge ever built.

But there was a flaw in Sir Horace's plan.

The curved arch meant the bridge could only ever open about 45 degrees

so the tallest ships

had to stay dead centre of the channel to clear it.

Not always possible with a sailing ship in high winds.

using Old London Bridge.

and Sir Horace's design was rejected.

A rethink was needed.

And Sir Horace knew just the man to do it.

To help make his ideas a reality,

Sir Horace brought in a brilliant engineer, John Wolfe Barry,

the son of the man who designed the Houses of Parliament.

He took Jones' ideas and turned them into a working bridge.

Barry scrapped Sir Horace's arch

and replaced it with the high-level walkways.

They meant the bridge could open fully,

Yeah, I think they come from Londoners, they are for Londoners.

to charities across London.

It's a fantastic system. Yeah, no, it's good.

There was a very deep philanthropic tradition

from the City of London Corporation.

Right the way back, you have historic figures

like Dick Whittington that actually represented that ethos

of giving to the other for the benefit of the city,

and I think that thread runs right through the history

of Bridge House Estates and City Bridge Trust.

So it is that Londoners looking out for other Londoners.

So in a way, those five bridges are a gift to London?

there's money available to distribute

This huge pot of money allowed architect Sir Horace Jones

and engineer John Wolfe Barry

to build in a solution to every objection.

In a sense, they bought off the opposition.

Today, Tower Bridge is far and away Sir Horace's most famous work,

but the terrible irony is he never lived to see it finished.

He died in 1887, just a year after construction began.

After his death, yet more refinements were made to his design,

particularly the towers.

His original bricks were replaced

So how does the income come into Bridge House Estates?

The whole operation was run from a building in Southwark

called the Bridge House.

The city used some of the money raised at Bridge House

to buy land called the Bridge House Estates.

The income from that land

was then used to pay for the upkeep of the bridge.

It was the start of a trust fund that is still going strong today,

eight centuries later.

I've come to the Guildhall, headquarters of the City of London,

to meet the man in charge of the money, David Farnsworth.

of the counterweight helps it open and close quickly and efficiently.

So you've got just over £1 billion in the assets of the charity.

Over £1 billion? Over £1 billion.

Which is rolled over the centuries

and then tolls from vessels going under the bridge,

people going over the bridge, properties on the bridge,

all generated money which got put into a pot

which was set up to maintain and repair five bridges

which are Tower Bridge, London Bridge, Blackfriars,

Millennium and Southwark bridges.

And when the bridge are sorted out,

horses and carts couldn't use them,

in a catastrophic tunnel collapse.

Despite that, it was a popular and financial success.

So, in 1869, another tunnel was dug,

almost exactly where Tower Bridge stands today - the Tower Subway.

This was once its northern entrance and in the 1890s,

it carried more than a million people across the river every year.

Sadly, it's been closed to the public for more than a century.

Today, it carries just water mains and fibre optic cables.

Despite their success in giving people a new way to cross the river,

the Tower Subway and the Thames Tunnel

both had a massive drawback -

cost six lives and nearly killed Isambard, too,

so they were both absolutely useless

in relieving the city's growing traffic jams.

In 1876, the Corporation of London was finally forced to act.

It set up a Special Bridge or Subway Committee

and opened a public competition to find a solution.

I have here some of the more unusual designs submitted to the committee.

There was this duplex bridge.

It's got a hexagonal roadway here in the middle

which would open on one side to allow a ship into the middle

before then opening up the other side.

Despite a new London Bridge replacing the medieval one in 1831,

and the port authorities insisted that the river must be kept clear.

Nothing could interrupt the operation of the port.

But the people who really needed the bridge were mostly poor,

the working class communities of the East End.

If they wanted to cross the river,

they were still stuck using London Bridge - and I do mean stuck.

Tens of thousands of carts, horses,

and people all had to travel for miles

and then possibly wait for hours

just to get from one side of the Thames to the other.

All the while on top, road traffic would keep flowing.

it was still in almost permanent gridlock.

Eventually, the traffic problems became so bad,

the people in power started to search for a solution.

And in 1843, father and son engineers

Marc and Isambard Kingdom Brunel offered one.

If a bridge couldn't be built over the Thames,

what about a tunnel under it?

It seemed like the ideal solution,

except tunnelling through the soft clay of the Thames riverbed was a nightmare.

The Brunel's masterpiece, the Thames Tunnel, took nearly 20 years,

You alright? Yeah. OK.

Sir Horace Jones, is called a bascule bridge.

Basically, it's a variation on the classic drawbridge

first developed to protect castles, towns and rivers in the Middle Ages.

Only bascule bridges add a clever twist to the tale.

A 'bascule' is French for 'seesaw', which is exactly how it works.

The problem with drawbridges, generally,

is that the huge weight of the bridge decks

makes them extremely cumbersome.

It takes a huge amount of energy to lift them.

And it can come crashing down really quickly,

potentially causing a lot of damage.

This design, by the architect of the City of London,

But just like any playground seesaw,

the secret to making a bascule bridge work...

..is a counterweight. You alright?

Even by adding a small amount of weight

to the back of the drawbridge,

as soon as it starts to lift,

gravity gives me a helping hand.

Making the bridge lift much easier

and giving my tired arms a bit of a rest too.

The genius of a bascule bridge is that the seesawing action

like Sir Joseph Bazalgette.

In fact, that's exactly what it says here.

"Facilitating the passage of large ships

"without stopping vehicular and general traffic."

Now, I quite like this design. It's quite fun.

But the committee decided it was just too complicated.

And here, this is the sub riverine arcade.

A huge tunnel, effectively, and it really is huge and ornate.

You can see the number of lanes that they've allowed through this tunnel.

More than 50 different ideas were submitted to the committee,

some from the nation's leading engineers,

ROB BELL: Britain's iconic bridges,

He sent in three.

But Sir Joseph's plans, along with all the others,

were rejected as unworkable, too expensive, or both.

For seven years, the committee sat on its hands until in 1884,

the architect of the City of London submitted this design.

And it is very familiar.

The two medieval castle-like towers,

the suspension bridge approaches on each side,

and the drawbridge here in the middle.

The only real difference that jumps out from this, for me, is the arch.