Original subtitles

and used on almost every major suspension bridge since.

Pieces just like that? It's incredible, isn't it?

I mean, to think that is what's holding up...

..well, us right now, this whole roadway, all the cars,

all the trucks that keep thundering past.

Yes.

That's marvellous.

So, the process of actually getting cables all the way across...

It's called spinning because they use a wheel

and the wheel is actually just a pulley.

The curious method of spinning was invented in the 1840s

by American engineer John Roebling

It's lots and lots of pieces like that.

It involves a pulley system that draws the wires across the span,

pulling them off a huge drum at one end.

Bill and I are going to recreate the principal

on a smaller scale, using string.

If you imagine a five-tonne reel of wire

fastened into the anchorage.

So this is me over on, let's say, the north...

Over on the north bank.

And then a spinning wheel pulling it.

So I run this right across... Right across the river. ..across the estuary...

And you'll see how fast this is unreeling. OK, yeah.

Firstly, if one of these wires should snap,

deep down into the concrete.

Anyone who ever said engineering was dull and ugly

has obviously never seen this.

It's absolutely beautiful.

The 404 wires in each bunch are hooked onto giant bolts,

each sunk 20m deep into the concrete wall.

Each of these loops was carried across the Humber individually.

There are nearly 15,000 lengths of wire in total.

If you were to drive across the bridge in a small car,

each of these wires would carry just about 30g of it.

All modern suspension bridge cables are made this way for two reasons.

And then it gets looped there.

there are still 14,947 remaining to hold the bridge up.

The other reason is that dragging a 70cm thick, 5,000-tonne cable

to the top of one tower

across a 1.4km gap to the other tower,

then down the far side would be impossible.

So, how was it actually done?

To find out, I'm meeting with Bill Harvey,

one of the engineers that worked on the job.

Getting those cables up is just amazing.

I mean, well, we're right under one of the main cables here.

What you can't see from here is actually what's inside this sheet.

To see how much the bridge moves,

Even though four wires could be spun in just 15 minutes,

it took 22 months to finish this part of the job.

In October 1979,

the last and most complicated major process could finally begin -

erecting the 21,000-tonne roadway, the deck.

This, of course, is what it's all about.

Everything else - the towers, the cables and the anchorages -

all exist just to carry this ribbon of highway across the water.

You might think that once the deck was in place

the whole suspension bridge would be solid as a rock,

but that's where you'd be wrong.

Standing on that.

even on a relatively calm day like today,

just watch this coin.

I've popped it down there,

right up against the edge of this expansion joint,

which connects the main bridge deck behind me

and the side span there.

Look at it go. You can see it's moving.

That's a good 2 or 3cm there already,

and it's the bridge deck where I am on this side that's moving.

It's the gentle flex and sway of the bridge in the wind

and with heavy traffic,

It's going to take about 15 minutes to do a trip,

And those bits get adjusted. Yeah.

And then another loop is taken.

So actually in that one journey across,

I've brought over two strands of wire.

And, actually, there are two wires on the spinning wheel as well,

so you've taken four and then you take another four.

Wow, so this speeds things up hugely. Yeah.

And then when you've done that 101 times -

and there's 404 wires -

you've got what's called a strand, and there are 37 strands up there.

How long would that...?

is where each of those bunches are anchor-pointed

done thousands and thousands of times.

To build up... Yeah.

..this great big cable that we've got here now.

And the guys who are working here just have to stand here

and maybe stand in the middle of the river on the catwalk

and catch the wires as they go past and anchor them.

So, you'd have guys dotted along. All the way along.

Just to kind of make sure and guide it and... Yeah.

Make sure everything is going correctly? Yeah.

And they'd be just stood up there, what, all day long? All day long.

Some of the things the guys used to wear.

the kind of all the infrastructure here...

Everything was there. ..went up with it. Yeah, you even had...

Well, you can see there, this is the canteen.

This is where the guys would have their lunch or whatever...

You know, if it rained.

So, what were the conditions like working on the bridge?

I mean, you were up there in all weathers, I guess.

If the weather was bad, you didn't go up.

It was brutal up there, especially with the wind-chill factor.

You could get down to -20, -30 up there.

Jeez. It was, it was cold.

And so as the towers grew,

I know one guy who used to pinch his wife's tights

because it would...to keep him warm in the winter.

It was a standing joke, the idea was if you climbed the tower,

it was 45 minutes and three cigarettes.

(LAUGHS) To get from bottom to top.

(LAUGHS)

The North Tower was finished in May 1974.

Next, they needed to repeat the slip forming process

and build the South Tower, this time, in the river itself.

But when engineers prepared to start work on the foundations,

they discovered a serious problem with the sheet piles

I'm meeting John Bailey,

that slip forming is quicker, cheaper and safer

than just about any other method of concrete construction.

In the years since, it's become standard practice around the world

for almost any kind of tower.

If you look here on one of the Humber towers,

you can see a series of horizontal lines

where the concrete was poured a few inches at a time.

It's almost like it's got a grain to it.

Working constantly, it took just under six months

to reach the full height,

that's an average of 7.6cm an hour.

surrounding the site.

a local man who had a bird's eye view of this building revolution.

John, you worked on top of the towers.

What was it like up there?

Initially, it was a little bit scary

because you were going into the unknown.

You'd never been up to that height before.

When you get up to over 500 foot,

then things look a little small from the top,

so, it was, yeah...

Your heart was in your mouth most of the time.

(LAUGHS)

than a 200,000 tonne slab of - well, you guessed it - concrete.

The titanic weight of this structure

and its partner on the opposite bank

is all that stops the two cables from crashing into the river.

But buried deep inside the anchorage is something totally unexpected.

Wow.

I mean, you know you're coming deep down

because of all the ladders, they just keep going, but...

..I don't think anything prepares you for this.

Just listen to that echo. (VOICE ECHOES)

Moo... (VOICE ECHOES)

It's really nothing more

In here, it's apparent

that the suspension cables are not two enormous wires

but actually thousands upon thousands of small wires,

each just 5mm thick.

Well, you can see

right above me here is where one of those main cables,

that runs the entire length of the bridge,

comes in to the anchorage.

And where it comes in, what was that great big, fat cable

splays out into 37 different bunches of wires.

And then these rows of orange blocks behind me

they had this second tower topped out in nearly half the time,

The design called for this man-made island

for the south tower to sit on.

But unexpectedly strong tidal currents ruined the sheet piles

they put in to build it,

helping cause a crippling two-year delay.

Work on the rest of the bridge relied on both towers being up,

but the sheet piles had to be reset

and the foundations dried out.

Project bosses were desperate to claw back some time.

Amazingly, with the experience they gained on the first tower,

and by working round-the-clock,

it's almost like it's breathing in and out.

increasing their average climb rate to almost 11cm per hour.

Building the entire bridge was supposed to take just five years,

but by 1976, four years into the project,

only the towers were complete.

The next major task was to lift the suspension cables

up to the top of the towers,

but unless they were securely fastened at each end,

they would quickly come straight back down again.

I'm descending into a tomb-like structure

at the bridge's southern end called an anchorage.

And that "the sections were swinging like seesaws,

But during the complex process of assembling the deck,

it was anything but stable.

And in March 1980, disaster struck.

At the north end of the bridge,

one of the 40-tonne cranes broke loose

and tumbled 70m down on to the incomplete roadway.

The joints ripped apart,

leaving two boxes dangling precariously.

The Hull Daily Mail reported the dramatic accident,

which happened just up here behind me.

Saying, "A man was hanging on for his life."

the more stable the bridge becomes.

"hitting each other with the sound like a clap of thunder."

It was a miracle nobody was killed

and, amazingly, the damage done was minimal,

but the whole incident was a very close call.

What could have been a catastrophic disaster

only set the timescale back by a few months.

In December 1980,

the final box was lifted into place,

completing the span.

The mighty Humber was bridged at last,

but it came at quite a cost -

This model is much more streamlined in shape,

lifting it slightly.

But gravity and tension in the cables pulled it back down

and, rather like a playground swing, up the other way.

The wind then amplified this movement,

pushing it further in the same direction,

then gravity and tension pulled it back even harder.

The back-and-forth motion got stronger and higher with each swing

until the bridge failed.

Change the design of the bridge deck and watch this...

It's the same fan, it's the same springs.

Let's see what happens.

£151 million in total.

allowing the air to flow over it far more smoothly.

Not much so far.

But it does something else that's remarkably clever.

It's the difference in lengths between the lower and upper deck

that has the strange effect of lowering the air pressure

under here compared to on top.

Now, effectively, that forces the bridge deck downwards,

pulling on the suspension cables.

The bridge is bracing itself into the wind,

and the windier it gets,

he was the first toll-paying car to go over.

I think I looked at my grandad the whole time and not her,

but, yeah, it was...it was a really good day.

I think now, you know, as years have gone by

that it's very much a focal point of the city

and in the people of Hull's, their hearts.

Her Majesty made the first official crossing.

Behind her, eager motorists queued up for their first turn.

The toll charge - £1.

Do you get a free toll pass? No. (LAUGHS)

No, 'fraid not. Even my grandad didn't.

Although he was the first person,

And so, I did that and she was very pleasant.

OK, very good. Yeah. Very good.

The Humber Bridge is perhaps a bit forgotten about,

slightly off the beaten track of Britain's motorway network,

but we should remember that, here in the UK,

we have a world record-breaking structure,

what was for 17 years,

the longest single-span suspension bridge on the planet.

And it is a bridge to be proud of

and to boast about

because we made it and we made it here.

Captions by Red Bee Media (c) SBS Australia 2019

I'm meeting Rachel Stainforth,

What's more, it had taken nine years instead of five

and thanks to the rocketing inflation of the '70s,

it was £81 million over budget.

Some people criticised the bridge as a white elephant,

a bridge from nowhere to nowhere,

that should never really have been built.

Despite all that,

this structure was celebrated as a national achievement,

the latest in a long line of groundbreaking British engineering landmarks.

And no less a person than her Majesty the Queen opened the bridge

on the 17th July 1981.

At Tacoma, a strong wind pushed the bridge to one side,

who was there that day, aged just six.

So, the Humber Bridge has been here ever since you can remember, Rachel.

It has. It's been a huge instrumental part of our family.

At the time, my grandad was chairman of the Humber Bridge Board

and my nan was Lord Mayor of Hull, so, because I was in the family,

I got asked to give the official bouquet to the Queen

on the opening of the Humber Bridge, so I was six at the time, I think.

And on the day, did it all go well?

I did have a bit of stage fright at the beginning

and so I had to have a nudge and said, you know, "Get on with it" sort of thing.

began to swing in a way no-one intended.

slowly drifting overhead.

Lifting the 17,000-tonne steel road deck into position in 1979

and keeping it there forever was going to be a serious challenge.

That's because suspension bridges have an invisible enemy -

the wind.

To resist the force of gales,

all of them are designed to allow sway,

but one chilling lesson from history illustrates

how this necessary flexibility can go badly wrong.

In 1940, a suspension bridge across the Tacoma Narrows,

just outside the US City of Seattle,

Like some kind of ridiculous space ship

Even before the bridge was finished,

it would buck like a bronco in high winds.

Construction workers nicknamed her Galloping Gertie.

Eventually, this curious ripple turned into a full blown wave

and just four months after it opened,

the entire bridge ripped itself apart.

There was something about the design of the roadway

on the Tacoma Narrows Bridge

that magnified the way it behaved in the wind.

Something the designers on this bridge had to completely avoid,

and the best way to see how they did it is by going down in here.

and blows down much more easily.

As cars and trucks thunder over the bridge,

they cause the deck to jiggle a bit.

But the bridge has to cope with a far greater force than traffic -

the wind.

And when the wind picks up,

movement in the structure is essential.

Imagine a tree and a brick wall in a gale force wind.

A tree bends and flexes,

it's much more likely to remain standing.

The brick wall acts like a huge sail,

takes the full force of the wind

I'm going inside the bridge deck...

Likewise, with a suspension bridge,

a bit of flex and sway is a good thing.

But if you get your sums wrong,

a bit of sway can turn into something much more extreme

and the whole bridge could come crashing down.

As slender and as elegant as it may seem from afar,

it's not until you get right up under the bridge deck, like I am here now,

that you get a true sense of the size

and the strength of this thing.

It's actually quite intimidating.

This one is much squarer

and it's the shape of that deck which ensures the Humber Bridge

will never gallop like Gertie.

Along the entire length of the bridge deck,

it's flat here in the centre above and below me,

and then it slopes away at the sides.

You can see it much better on this model here.

So underneath, it's shaped like a saucer,

and over the top, it's shaped, well, like an upside down saucer.

Compare that then to this model here of the bridge deck

of the ill-fated Tacoma Narrows Bridge.

You can see they're very different.

to form a continuous deck,

and it's got these solid side barriers all the way along.

So, let's see what happens to this with a little bit of wind.

Now, you might expect the bridge deck just to be pushed away by the fan

and kind of stay there until I turn it off,

but give it a sec.

It starts to sway gradually,

but it doesn't take long

for the Tacoma model to waggle erratically.

But look at that.

It's going absolutely berserk, it's osculating back and forth.

It's a phenomena called flutter.

and then another kilometre all the way down

(LAUGHS)

(LAUGHS)

So, you leave the day light behind,

coming right down into this huge, cavernous void.

(LAUGHS) (LOUD RUMBLING OVERHEAD)

And it's noisy too with the cars and trucks going overhead.

They're literally right overhead, just there.

This is the middle of the bridge deck.

It's a series of these vast, hollow, steel boxes,

which continue for a kilometre in that direction,

along to the north side of the river,

The Humber Bridge towers proved

back in that direction, too, over to the south bank.

(LAUGHS)

It's really odd down here.

Each one of these boxes was pre-fabricated on land,

but getting them into place was no easy feat.

Starting at the dead centre of the bridge,

they were floated into position,

then hoisted one by one with huge cranes,

which themselves hung off the suspension cables.

Each box was then welded to its neighbours

that the bridge really got built.

it was the longest single-span suspension bridge ever built,

with a road deck 2.2km long.

This new roadway connected communities

on opposite banks of the estuary

that used to be 70 miles apart by road.

Overnight, they became brand-new neighbours.

But more than that,

this record-breaking bridge formed the promise of a new future

for this part of Britain.

It would spur the creation of a new industrial hub for the nation.

But it wasn't quite for such public-spirited reasons

When the Humber Bridge opened in 1981,

It's widely held that it was, in fact, the result

of some rather more calculated political game-playing.

Back in the 1960s,

the folk of the Humber towns had already spent decades

campaigning for a new bridge.

Theirs was the only estuary in Britain that didn't have one.

But a bridge that could span this expanse of water

would not only have to be extremely long,

but also very tall.

There are four major ports on the Humber

that carry a hefty 13% of the UK's seaborne trade between them.

The Tattershall Castle put in 39 years service on the Humber,

It was built in the 1930s.

If you look you can see all these beautiful brass fittings,

this great big crank shaft and connecting rods.

And down here, you can see where the spindles would be attached,

and there would be another one on the other side,

and they'd head straight out to drive the great big paddles

on each side on the outside of the hull.

Sadly, the paddles have long since been removed,

but you can see the deck extensions that once sat above them.

These images show the steamer in its final days

under the ownership of British Rail.

With 4,500-tonne cargo ships regularly passing the bridge,

before being brought to London in 1975.

But the fact that this old paddle steamer should end up

here on the River Thames is oddly fitting.

You see, it was right there,

in the Houses of Parliament behind me,

that this ferry lost its job on the Humber.

It was a casualty of a fierce political struggle

that saw the voters of Hull being offered

what was seen as an extraordinary election bribe -

a bridge.

A bridge that was set to be the longest in the world.

Mrs Castle stood up to give a speech to 200 people

This man died.

Henry Solomons MP.

Harold Wilson's Labour Government was made highly vulnerable

by the death of Mr Solomons.

A by-election for his Hull North seat was set

for the 27th of January, 1966.

If Labour lost, Wilson would be left with a majority of just one MP.

For Labour, a win was crucial.

Wilson dispatched his most experienced political operators

to win over the voters,

including the transport minister, Barbara Castle.

all of a sudden, worth it to the Government.

crammed into a local school hall.

Everyone expected some kind of road improvement carrot to be dangled,

but then she came out with six words that nobody anticipated -

"You will have your Humber Bridge".

Nine days later, the people of Hull went to the polls,

and here at the city hall, the votes were counted.

MAN: Joseph Kevin McNamara, Labour, 24,000...

(CHEERING)

It was a victory for Labour.

The bridge would finally be built.

But six years later, when Wilson was voted out of office,

A suspension bridge could cross the water in one giant leap,

the deck had to be high enough to allow them to flow underneath.

But the design also had to take into account

what goes on under the water.

The Humber Estuary has a very soft bed,

with deep channels and shallow banks that can shift over time.

As those deep channels move,

the shipping lanes need to move with them.

Most kinds of bridge able to span a river this size,

require a whole series of supports,

leaving only narrow gaps for shipping that could easily silt up.

But there's one type of design that needs just two towers.

Now, this is the engine room.

allowing ships to follow the channels as they change.

So to keep the full width of the estuary open,

this bridge had to be a suspension bridge.

And with the banks more than 2km apart,

it would be the longest single-span ever.

Despite their advantages,

suspension bridges are complicated and, therefore, costly to build.

No-one seemed willing to spend the kind of money needed.

Then something happened

that would make the expense of such a construction,

they're about 70cm thick.

It's so high up.

It's nothing apart from these two cables which disappear off.

(LAUGHS)

This is the Humber Bridge.

Its length from end to end is more than 2km,

and between the two gigantic towers,

stretches one of the greatest engineering feats in history.

The suspended central span is 1,410m long,

and when it opened in 1981,

it was the biggest suspension bridge on the planet.

Just look at these two enormous cables,

This is something special.

Each of them weighs over 5,000 tonnes.

Then there's the towers,

the one on I'm stood on here on the north side,

and the one way off in the distance.

These things are so tall,

they're actually further apart at the top than they are at the bottom.

And you know why?

Because of the curvature of the Earth,

that's the scale we're talking about here.

The whole thing is epic.

For nearly two decades,

Stopping traffic.

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 constructions.

this colossal edifice reigned supreme.

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.

On the eastern fringes of the British Isles,

there's an extraordinary structure that is somewhat forgotten.

It's a record-breaking structure that changed engineering forever,

and we've been given special permission to explore it,

from bottom to top.

Oh, wow! Oh, my goodness!

The paddles on the steamer allowed them to navigate very shallow waters,

This is Yorkshire.

Across the other side, away over the expanse of the bridge,

is the south side of the estuary.

That's North Lincolnshire.

And if you look out east, you've got the town of Grimsby,

and further east, you're into the North Sea.

Before the bridge was built,

driving from one side of the Humber to the other

involved a 70-mile road journey that could take two hours or more.

The only way to cross quicker,

was to ride on Britain's answer to a Mississippi paddle steamer.

Off in the distance there, the city of Kingston upon Hull.

but the silty Humber was so shallow in places,

the ferry still ran aground from time to time,

stranded in the middle of the estuary until the tide changed.

Amazingly, decades since it was put of a job on the Humber

when the bridge opened,

you can still hop aboard one of the paddle ferries today,

here on the banks of the River Thames in London.

Now, permanently moored, and used as a popular bar,

the Tattershall Castle, as this vessel is known,

is in remarkable condition.

Stepping aboard is like walking into a long forgotten world.

As with most great bridges,

The longest span of any suspension bridge in the world.

For many, including me,

the Humber Bridge is one of the most beautiful bridges ever built.

There's an understated simplicity that I just love.

The way it disguises thousands of tonnes of concrete and steel,

like a feather floating effortlessly across the water.

But building this record-breaking bridge was far from effortless.

It was a severe technical challenge,

born out of an extraordinary political power struggle.

So just what did it take to build the longest bridge in the world

right here in Britain?

there was still no bridge.

the story of this one begins with a stretch of water

that many people thought unbridgeable -

the wide Humber Estuary.

Formed by the combination of two great rivers,

the Ouse and the Trent,

and almost 60km long,

this tidal inlet divides a major industrial region in half.

Let's have a little look at the lie of the land.

So I've come up the north tower,

so this is the north side of the estuary.

totally changed its behaviour.

like when a heavy lorry

crosses a suspension bridge,

could cause it to crack apart.

Monier found this same problem

when he tried to drag his orange pots around the garden,

until he made a simple change to their design.

Monier discovered

that if he put iron rods into the concrete as it set,

when it hardened, it was much stronger.

That simple addition -

adding metal rods to create reinforced concrete -

So any sideways pull,

This new form of concrete

is as strong in tension

as it is in compression,

making it perfect

for almost any kind of structure.

By the middle of the 20th century,

architects and engineers were finding amazing new ways

to exploit its properties.

The engineers at Freeman Fox wanted to take that one step further.

They knew using reinforced concrete instead of steel could save

months of construction time and millions of pounds

The Humber Bridge is still standing today,

They used it on the world-famous Pantheon in Rome.

Its dome is one of the biggest in the world made of concrete,

and it's been standing for nearly 2,000 years.

But suspension bridge towers are subject to quite different and far greater forces

than most buildings.

The thing was, up until that point,

suspension bridge towers had almost always been made out of steel,

so the bridge designers had to be absolutely certain

that a huge concrete tower would be equivalent in strength,

and the reason they could be was all to do with these.

Oranges.

if they could find a way to get it into place quickly and safely.

thanks to a French gardener called Joseph Monier.

It was the 1860s

and Monier worked at the historic Royal Palace in Paris

where one of his jobs was to look after the exotic citrus plants.

Every summer, he'd have to move them from inside their glasshouse

to the gardens outside,

but the concrete pots they were in kept breaking.

The problem is that whilst concrete is very strong

under the force of compression,

it's very weak under the force of tension.

called the Landmark.

and remained the longest unsupported roadway until 1998.

One of the challenges facing the bridge's designers at Freeman Fox

was the massive towers that such a structure needed.

They would be some of the tallest ever built from concrete,

but most existing methods for pouring the concrete just weren't suitable...

..so they took a punt on a novel technique.

The technique enabled tall structures to be built quicker

and more efficiently than ever before.

It was called slip forming.

Slip forming gained popularity in the 1960s

after being used to build a 31-storey tower in Las Vegas

It used new materials, and groundbreaking methods

Building a giant, 155m-high mould,

then pouring concrete from the very top

would be technically challenging,

really costly, and take far too long.

But slip forming needs only a small mould, about 6m high.

As the lower parts of the new tower dry and harden,

the mould is shifted, or slipped, up a few centimetres on jacks.

All the while the concrete is poured without interruption.

The mould moves continuously upwards,

leaving behind a single, solid structure.

The technique worked impressively.

and pour concrete in from the top.

Because even if the concrete itself was up to the job,

most methods of casting it weren't.

A typical way to make a concrete structure was

to pre-cast it into small pieces

and hoist each one into position by crane,

one by one.

But that was out of the question

with the kind of heights they were talking about here.

Hey! (CHUCKLES)

Another option was to cast the entire structure in-situ,

but you can't build a 155m-high mould

The Romans were the first large-scale users of concrete.

So, that's when they turned

to another fashionable, new building technique.

It was called slip forming and it had proved successful

in building a futuristic hotel and casino in Las Vegas.

But could Freeman Fox transplant this technology

from the parched Nevada desert to the watery world of the Humber?

It was a gamble they just had to take.

The Humber Suspension Bridge,

with its world record-breaking span across the Humber Estuary,

it's a triumph of 1970s engineering.

And what I've created here is much more of a...

The answer is to start where every suspension bridge must,

with two enormous holes in the ground.

These holes will form the foundations for the towers.

The towers will then be used to hold up the suspension cables,

and from those cables, the road deck will be suspended

from a series of smaller vertical cables

called hangers.

But it all starts with the holes,

and digging those is not as easy as it seems.

If you've ever dug a hole on a beach before,

you know it doesn't take long before it starts filling up with water.

with a 2km road hanging off it?

..murky pond than any kind of basis

for a 155m suspension bridge tower.

The way to make a dry hole on a wet beach is to use sheet piles.

These long interlocking strips of steel are literally hammered

into the ground to create a curtain of metal.

On the Dutch River, one of the Humber's tributaries,

Phil Boyes of the Environment Agency is driving piles into the riverbed

as a flood defence.

As one sheet goes down right next to the other, they kind of join, do they?

There's a bit of a joint between them? There is, yeah.

On the edge of each pile, there's what is called a clutch.

His other hits include the Severn Bridge

Surprisingly, the man who defeated him,

Conservative Prime Minister Ted Heath,

revived the scheme.

Heath had plans for a new industrial county

called Humberside.

It would take in the whole estuary

from Hull to Grimsby, and beyond,

with a new bridge at its heart.

Leading the project would be the firm of Freeman, Fox & Partners,

run by Sir Ralph Freeman.

Freeman was the world's best suspension bridge engineer.

So, one is...it's a curve of steel one way

and the Forth Road Bridge.

If Sir Ralph could make this ambitious design a reality,

it would be the pinnacle of his career.

Ground was finally broken in July 1972.

If you stand here and look out

over what was the biggest suspension bridge in the world,

you might have a job puzzling out just where they started building it.

I mean, how do you get two enormous cables

weighing 5,000 tonnes,

155m up in the air,

they'd now cast a huge slab of concrete into the hole -

At the Humber Bridge construction site,

hundreds of tonnes of sheet piles were driven deep into the riverbed,

forming a dam of steel around the location of each tower.

That allowed diggers to excavate the area inside the dam,

without fear of the walls caving in

or the hole filling with water.

Once the hole was deep enough,

the next major step could take place - filling it in again,

because a strong foundation made of solid concrete was needed

to support the first of the two towers.

A year and a half into the project,

Everyone's happy. Job well done.

44m long, 16m wide and 11m deep.

It's still there, hidden away under the beach.

And so, the time had come to begin

the first really revolutionary feature of the bridge -

a 155m-tall tower,

to be made, for the first time anywhere

on a long-span suspension bridge, out of concrete.

Concrete is magic stuff.

When it's first mixed,

it can be poured or moulded into almost any shape.

And when it sets, it's as tough as stone.

Yes, that's the one. Here we go.

and then it's curved the opposite way on the next pile,

so that helps the two piles interlock.

And then the vibrating hammer essentially just vibrates the pile

at a very high frequency

and that's what helps drive that pile down into the ground.

Essentially, it's using brute force... It is, yeah.

..to get this sheet down into the ground.

That's very clever.

Now I understand the idea behind pile driving,

Phil is letting me put the theory into practice.

So, by doing that we're going to, what, just build up the pressure in the hydraulics?

ROB BELL: Britain's iconic bridges,

Away it goes.

(LAUGHS)

And down it goes, I mean look at it!

What is here just a small flick of a switch...

..triggers an enormous amount of power over there.

This is high-tech equipment doing its job.

It's powerful, it's unforgiving, and it's bloomin' loud.

It's the Gordon Ramsey of the construction industry.

Here we go, look, that's it. That's the signal.

Just giving it a quick check there to make sure it is nice and level.