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00:01The Houses of Parliament in London.
00:04One of the most iconic structures on the planet.
00:07This wasn't just building a building.
00:09This was a major piece of engineering.
00:11Mysteries and secrets lie beneath the skin of this megastructure.
00:15It's the most remarkable building in the world.
00:18How did its creators push technology to the very limits
00:23and invent the blueprint for modern skyscrapers?
00:26What keeps the world's most famous clock in perfect time?
00:30And how does it survive all that Mother Nature can throw at it?
00:35The only way to solve these mysteries
00:38is to blow this immense palace apart brick by brick
00:42and dismantle its famous clock tower cog by cog.
00:47Diving deep through its wall and vaults
00:50will help us unearth the astonishing secrets
00:52at the heart of this Victorian wonder.
01:04Standing on the banks of the River Thames in the heart of London, England,
01:09is the Palace of Westminster,
01:12better known as the Houses of Parliament.
01:17A labyrinth of more than three miles of corridors,
01:22connecting more than 1,000 grand rooms, chambers, and vaults.
01:28This site has been the home of the British government for centuries.
01:34It's built to look like a giant medieval castle,
01:38but it hides many modern secrets.
01:44This immense palace was completed in 1870.
01:48It has more than 1,000 rooms spread across eight acres.
01:52It has three spectacular towers.
01:56To the south, the Victoria Tower,
01:58the tallest square tower in the world when it was completed.
02:02In the center, the huge spire has over 2,000 panes of glass.
02:08And to the north, the iconic Big Ben,
02:12home to one of the greatest timepieces the world has ever seen.
02:19An engineering marvel, when it was constructed,
02:22this was one of the most advanced buildings on the planet.
02:28An army of workers keeps the Houses of Parliament running.
02:33And today, a multi-billion dollar restoration project is underway.
02:38Upgrading the building's roof,
02:42stonework,
02:44and ornate interiors.
02:47The project is helping to unlock the Victorian mysteries
02:51of the Houses of Parliament.
02:54Chief among them is the clock tower,
02:57a pioneering display of engineering genius better known as Big Ben.
03:08How did the Victorians make the world's largest, most ambitious clock
03:13and have it run on time in a tower almost 300 feet tall?
03:20Inside the tower, it is master clockmaker Ian Westworth's job to keep Big Ben running on time.
03:27We've got 334 stairs in the clock tower and no lift, unfortunately.
03:36It's a task that takes him behind the face of this famous landmark and into the heart of this clock's
03:43extraordinary mechanism.
03:49Inside this iconic clock tower hangs Big Ben itself,
03:54the nearly 14-ton bell that gives the tower its nickname.
03:58The bells that chime on the quarter hour sit around it.
04:02Their strikes are controlled by the intricate ticking mechanism at the heart of the tower.
04:07It keeps the clock accurate to within just two seconds a week.
04:12On each side, 312 shards of opal glass make up the clock face.
04:19The copper minute hands are 14 feet long, as tall as a double-decker bus.
04:24These famous dials have kept London running on time for 160 years.
04:33Like any ordinary wristwatch, this clock needs winding, just as it did in Victorian times.
04:40Put the winding handle on, and then winding for about the next hour and a half.
04:48When Parliament commissioned this clock in 1854, they insisted Big Ben be the biggest, most powerful chiming clock in the
04:55world.
04:59And most challenging for the designers, accurate to within two seconds per week.
05:06But there was a problem with making such a giant clock accurate.
05:10The clock makers of the day said you just couldn't do it.
05:12Our minute hands are 14 feet long.
05:15So in a good gust of wind, they act as like sails.
05:19And clocks before this time, the wind would catch the hands, and the hands would drive back and make the
05:24clock inaccurate.
05:27How did the Victorians design a clock that could resist the wind?
05:36The secret to stopping strong gusts blowing the hands out of time
05:40is a set of heavy weights that pull the hands around as they drop.
05:46Two swinging arms keep the weights dropping at the correct speed by pushing the pendulum,
05:51which sets the ticking speed of the clock.
05:57The pendulum turns a ratchet wheel once every second,
06:03which releases the weights by a precise amount,
06:09so they can pull the clock hands around at exactly the right speed.
06:19The Victorians had stopped the wind from affecting Big Ben.
06:23But with any clock, minute changes in the atmosphere could also impact the mechanism.
06:30And the bigger the clock, the bigger the risk.
06:34Today, Ian uses technology that Victorian clockmakers could only dream of.
06:40A system of sensors hooked up to a computer allows him to monitor the tiny atmospheric changes.
06:50We've got temperature in the clock room, which we monitor all the time.
06:54The green line tracks changes in temperature that cause the mechanism's metal to expand and contract.
07:00These, just these little blips on the temperature are people coming in.
07:05That's how accurate we're actually monitoring what's going on inside the clock room.
07:09Another sensor allows Ian to check the effect of these temperature changes on the pendulum.
07:15At the bottom of the 14 and a half feet long pendulum, there's an optical sensor.
07:19Every time the pendulum breaks the optics, it sends a message to this laptop.
07:24The pendulum should be breaking it every two seconds.
07:27And the brown line down the middle is telling us exactly how close to two seconds we are.
07:33At the moment, we're running at 2.00012.
07:39She's doing absolutely fantastic, apart from being a little bit slow.
07:44Ian thinks that the day's temperature changes have caused this inaccuracy.
07:49It may be small, but without expert intervention, it will knock the clock five seconds out of time in a
07:55single day.
07:57Ian checks if Big Ben is on time.
08:02He gets an accurate reading of Greenwich Mean Time and then heads to the Belfry.
08:08It's currently almost 10 a.m.
08:11Will Big Ben chime on time?
08:15So what you'll see, this is the first hammer that moves, so it doesn't come as a shock.
08:21If you watch that one, it'll lift up and drop and play the 16 notes.
08:25Then there's a pause of about 10 seconds and then that one will go.
08:29It'll be any moment, now.
08:56Big Ben's chime roars across the Capitol at 118 decibels.
09:01Almost as loud as a jet plane taking off.
09:05You can feel the vibration of the bell throughout the whole bell frame.
09:09When the bell was first fitted, you could hear it 10 kilometers away.
09:14Nowadays, you'd be lucky to hear it half a kilometer away across the river,
09:18because there's so much noise in London now.
09:24So, is the clock on time?
09:26We're one second slow.
09:28With the temperature affecting Big Ben this much, Ian needs to bring the clock back up to speed.
09:35But how can he adjust the time on a clock that's got 14-foot-long hands?
09:40Ian knows the secret that has been passed down from Big Ben's original clock keepers.
09:46Traditionally, what we do, we add a penny.
09:50One penny, old pre-decimal coin, speeds the clock up just to bring the clock back into time.
09:57Like those original clock keepers, Ian knows this tiny weight raises the pendulum's center of gravity and makes it swing
10:04faster.
10:05We've corrected it and it's come back up to time.
10:08That's pretty good for a 160-year-old clock.
10:11With the mixture of Victorian know-how and modern technology, Ian keeps Big Ben in perfect time.
10:22The clock stands in a nearly 9,000-ton tower that rises from London's soft, gravelly earth.
10:30How did the Victorians stop this behemoth tower from collapsing on such unstable ground?
10:36And how has it survived as the city has expanded beneath it?
10:45The Houses of Parliament in London.
10:47The most technologically advanced building of its age.
10:52An army of experts keeps this structure running, revealing its Victorian secrets as they go.
11:00For over a century, Big Ben has been the ticking heart at the city center.
11:05A triumph of engineering.
11:08Supporting this groundbreaking clock requires a tower that's equally magnificent.
11:16Made from over one million stones and bricks, this tower is enormously heavy.
11:2438 tons of iron tiles sit on top of the spire.
11:28Beneath them, the bronze bells weigh 24 tons.
11:33The clock mechanism is as heavy as a military truck.
11:38To hold up the colossal structure, nearly 9,000 tons of stone and brick,
11:44the Victorians built a concrete foundation, almost 10 feet thick,
11:48to stop the towers from sinking into the wet sand beneath.
11:52These solid foundations have kept this London landmark standing tall for 160 years.
12:00But the challenges facing Big Ben were not over when construction finished.
12:06London is constantly rebuilding itself.
12:09And its subterranean rail network, the underground, is ever expanding.
12:16Today, the construction of new train tunnels poses a constant threat to buildings on the surface.
12:22The last thing you want is structures above ground moving because of what you're doing below ground.
12:29Jeff Morris is one of the London Underground's engineers.
12:32He knows just how dangerous tunneling can be.
12:35The worst-case scenario would be collapse.
12:39In 1994, the London Underground excavated new train tunnels just 90 feet from the base of Big Ben.
12:47As tunneling progressed, engineers were alarmed to detect movement in the buildings above.
12:56There was a problem with the ground movement because of the foundations becoming destabilized.
13:03The engineers faced a challenge.
13:05They needed to stop Big Ben's clock tower from tilting, fast.
13:09But the problem was bigger than they realized.
13:12The Earth under Big Ben is extremely unstable.
13:16If you've been to the seaside and you try and dig a hole,
13:18it just instantly fills up with water and grows wider instead of deeper.
13:22Then that is typical of the gravel and the ground conditions at Westminster.
13:27You need something that's going to work very quickly.
13:34As the 24-foot-wide train tunnels ran close to Big Ben's foundations,
13:40the tower began to lean.
13:43To keep it stable, engineers dug a deep shaft
13:49and pushed long steel tubes into the ground right beneath Big Ben.
13:55Each tube had 600 valves,
13:59so workers could pump in a concrete mixture to fill the cracks in the ground with precision.
14:05As the engineers dug the tunnels, they injected over 220 tons of concrete mixture,
14:11successfully stopping Big Ben from becoming a leaning tower of Pisa.
14:18Once they stabilized the ground, it would have stopped any potential further movement on the clock tower.
14:24One of the key ingredients into successful tunneling.
14:28This ingenious intervention kept the tower standing upright and the bells ringing on time.
14:40Experts may have saved Parliament from dangers below ground,
14:44but now a bigger problem threatens it from above.
14:47After 160 years covering the Houses of Parliament, the roof is failing.
14:53Work to restore it goes on day and night.
14:58No instructions for building this roof survive from Victorian times.
15:05As engineers dismantle the 65,000-square-foot roof structure,
15:10they're uncovering the secrets of its intricate design.
15:15Elton Bilton is in charge of the operation.
15:21How's that looking, alright?
15:23Elton and his team have to remove and repair every single tile.
15:28We're busy stripping the roof, taking all the old tiles off.
15:32These old tiles that have been on the roof for over 100 years,
15:36they are damaged and in a bad state.
15:42After surviving London's weather for an incredible 160 years, restoration is now critical.
15:51It's a dangerous undertaking.
15:54Each tile weighs between 40 and 50 kilograms.
15:58You wouldn't want a tile like that falling on your head.
16:01They've got sharp edges and they're very heavy.
16:04Elton removes the tiles so he can send them away for repairs.
16:11They may look the same, but every single tile is unique.
16:15Putting the repaired tiles back will be an enormous jigsaw puzzle.
16:20Before anything gets removed from the roof, each and every component has a unique number.
16:24Otherwise it would be chaos and we wouldn't know where to put things.
16:28Using this process, once the tiles are restored, Elton will reassemble the 7,000 tile roof exactly as the Victorians
16:35intended.
16:36Okay, that tile is now ready to go back to the factory for restoration.
16:42Why did the Victorians build the roof with such a complex design?
16:50The answer lies in a 19th century disaster.
16:55At this training center, 50 miles from Parliament, firefighters think they know what happened.
17:01Is everybody fit and well to take part in this live fire exercise?
17:04Is there a positive response from you all?
17:05Yes, sir.
17:06The original houses of Parliament were a collection of medieval buildings that had stood on the Thames for almost 1
17:12,000 years.
17:15But in 1834, a fire broke out in Parliament that caused destruction on an unprecedented scale.
17:21The sudden fireball was so bright, it was seen 25 miles away.
17:30The big mystery, what caused such a devastating explosion?
17:36Physicists are on the verge of a groundbreaking revelation.
17:39Could a new discovery destroy everything we think we know about the universe?
17:44Don't miss.
17:45Hunt for Particle X.
17:47Next Tuesday at 10 on Science.
17:50We don't know what lurks in the shadows.
17:55It's like nothing I've ever seen before.
17:58What on Earth is going on?
18:00NASA's Unexplained Files. Season premiere August 30th at 9 on Science.
18:14In London, Pauline Holden trains firefighters.
18:18She thinks the 1834 explosion at the Houses of Parliament was triggered by a deadly phenomenon called a flashover.
18:26A flashover can occur extremely quickly, within minutes.
18:30As fire heats the combustible materials in a room, they release flammable gases.
18:36If these gases are trapped in an enclosed space,
18:40when the fire reaches a critical temperature, there's one possible outcome.
18:46Fire makes the gases explode into a fireball.
18:54This is a flashover.
18:57Back in 1834, Parliament's buildings were made from stone.
19:03But the roofs were made from wood.
19:07The flashover ignited the wooden roofs, spreading the blaze with astonishing speed.
19:14Firefighters battled in vain.
19:17The fire destroyed the Houses of Parliament.
19:20Britain's government needed a new headquarters.
19:24And this time, it would be fireproof.
19:32Inside another section of the roof structure,
19:35Palace architect Adam Wotrovsky is investigating how the Victorians ensured
19:40their Parliament would never burn to the ground.
19:45After the Great Fire of 1834, one of the priorities in rebuilding the new Palace of Westminster
19:52was to make it as fireproof as possible.
19:54And this remarkable roof is part of that fireproofing exercise.
19:58The Victorian engineers took advantage of a new building material.
20:02The frame of the roof and tiles are all made from cast iron.
20:07Cast iron had never been used on this scale before.
20:10With a melting point of 2300 degrees,
20:14this cast iron roof would hold up when a timber roof would just burn.
20:18The cast iron roof used cutting edge technology both in terms of the materials and the construction,
20:23with of course not a computer in sight when it was designed.
20:26So this was a huge experiment.
20:29Pulling this off was a great challenge.
20:32Cast iron is extremely heavy.
20:33So how did the Victorians design this roof so that it wouldn't collapse in on itself?
20:41The secret lies hidden inside.
20:46The 7000 cast iron tiles that cover the entire palace add over 386 tons to the weight of the roof.
20:55But each tile has a clever design, which allows them to become exceptionally strong as they lock rigidly together.
21:07Underneath, a lightweight skeleton of trusses is enough to hold the roof aloft.
21:11The trusses add very little additional pressure to the walls below, creating this unique system that still protects the Houses
21:19of Parliament to this day.
21:27In these vast workshops in South Yorkshire, workers are preparing the iron tiles that have come off Parliament's roof for
21:34restoration.
21:35The original engineers could never have predicted how a century of London's weather would affect this unique roof.
21:43Workers blast the tiles with particles of steel, removing the rust and grime to reveal any holes or fractures in
21:50the iron.
21:52Repairing this damage is the most important stage of the restoration.
21:58It's a highly specialized job.
22:03To do this kind of job, you do need a steady hand.
22:07Danny Whitworth is in charge of fixing Parliament's roof tiles.
22:12If you put heat in one area pretty quick, that's when you get your cracks appearing.
22:19Danny applies bronze at over 1500 degrees into the defects in the tile.
22:24This restores the tile's strength.
22:27You should get a bit of heat into the tile.
22:30But applying too much heat could cause the brittle iron to crack.
22:35We're hoping really that we don't want the tile to crack.
22:39When you start getting cracks appearing, it just seems to kind of run on and on and get pretty difficult.
22:46If that starts to happen, then normally we'll end up replacing the tile.
22:49With one slip of the hand, Danny could ruin the 160-year-old tile.
22:55They prefer to try and keep as much old material as possible rather than using no materials.
23:01It's kind of restoration rather than replacing the stuff that we're doing.
23:05It's a lot better if we can repair it than have the tiles replaced.
23:15I'm happy with that. It looks good. It's nice and clean.
23:22Once repaired, the tiles are returned to the Houses of Parliament, ready for Elton to install on the roof.
23:34That's a perfect fit. If they all fitted like that, we'd be very happy.
23:39This roof should last for another 80 to 100 years.
23:43Thanks to Elton's team, another section of the roof is complete.
23:47Job well done, I'd say.
23:51The Palace's all-iron roof was a unique engineering solution.
23:57But its Victorian creators wanted to push Parliament to record-breaking heights.
24:03To do this, they had to invent a radical new way of building and take on the River Thames itself.
24:17Britain's Houses of Parliament, a building light years ahead of its time.
24:23Today, experts are deciphering the mysteries of its Victorian design.
24:30At its southern end soars the extraordinary Victoria Tower.
24:33It stands 320 feet high, even taller than Big Ben's clock tower.
24:40Yet at its base contains a vast open ceremonial entrance.
24:46How did engineers build this 320 foot high megastructure
24:52and support its nine floors above this empty space?
25:00The traditional bricks and stones hide a secret, an immense iron skeleton.
25:07A network of tapering columns, each 200 feet tall, supports the weight of the building's floors.
25:17The columns channel this immense load down to a base made from 13-ton girders.
25:23It transfers the weight of the floors onto four external walls, leaving an immense stone vault below.
25:31The Victoria Tower's engineering was decades ahead of its time.
25:39This tower was the inspiration for one of America's earliest skyscrapers,
25:45the Woolworth Building in New York.
25:48Its iron skeleton was a vital step towards developing steel-framed skyscrapers in the 20th century,
25:55which went on to dominate not only New York's iconic skyline,
26:00but cities across the world.
26:04The Victorians had built a precursor to modern skyscrapers.
26:08But why did they need to construct such an extraordinary structure?
26:18Deep inside the Victoria Tower holds Parliament's most precious treasures, just as it did when it was built.
26:26Around us we can see 64,000 Acts of Parliament, dating back to the 15th century,
26:32stored in parchment scrolls, one scroll per act.
26:37All the laws that have been passed by Parliament over the centuries.
26:42Archivist Caroline Shenton guards these priceless laws.
26:45It's an amazing space and air-conditioned to 16 degrees centigrade and 55% humidity,
26:53which helps to keep all these incredible scrolls at the right temperature to preserve them for the future.
27:00Storing all of Parliament's documents and laws pushed the Victoria Tower up to its record-breaking height.
27:09But building big was a huge challenge.
27:12Back in 1834, as today, roads and historic buildings surrounded the site on three sides.
27:19There was no space for the scaffolding or cranes that could create such a vast tower.
27:24The Victorians needed to invent a radically new way of building.
27:31Engineers hit on an ingenious solution.
27:36To use a giant rising platform and build the entire tower from the inside out.
27:42Eight men hoisted up the 44-ton platform, cranking the gears in six-foot bursts.
27:53On top, a crane lifted the four tons of stones from the ground to the platform.
27:58Powered by a steam engine, it could deliver ten loads an hour.
28:04Two more cranes placed the heavy stones in position on the tower walls.
28:08To observers, the tower appeared to grow effortlessly under its own steam.
28:15This innovative construction technique solved the engineers' problem on one side of the palace.
28:20But on the other side, they had to contend with an even greater adversary.
28:26The River Thames.
28:27The River Thames.
28:30At Parliament's River Wall, where the Houses of Parliament meets the River Thames,
28:36structural engineer Alistair Lenkner investigates how the Victorians created the space they needed for the new Parliament.
28:43They worked out that the size of the building they really needed was actually a lot larger than the space
28:49that was available.
28:50With roads and buildings surrounding the site, Parliament's designers could only expand in one direction.
28:56So if we consider this area here, it's the foundation of the new building design.
29:05But this line here is the line of the riverbank at the time.
29:11So we could see that all this part of the building had to be built out into the existing tidal
29:16River Thames.
29:17To build on this land, Victorian engineers needed to reclaim it from the river.
29:23It was a huge challenge that called for a trailblazing construction plan.
29:37To build London's Houses of Parliament, engineers had to reclaim land from the River Thames.
29:42First, they took twin rows of timber piles, each 36 feet deep, and drove them into the riverbed.
29:49Then they fixed sheets of steel between the piles to create two barriers.
29:53Each barrier was over 790 feet long.
30:00The engineers filled the space with clay to create a watertight wall called a cofferdam.
30:11Finally, they drained the trapped river water and filled the space with concrete to form the foundations of Parliament.
30:21The final challenge was to replace the temporary cofferdam with something strong enough to withstand the mighty Thames.
30:29So once the cofferdam had been built and created the dry space behind it, that allowed them to start construction
30:35of the permanent river wall.
30:37This wall needs to protect Parliament from the extreme pressures of the rising tide.
30:43The secret to the strength of the river wall lies in its shape.
30:47The high tide, the pressure gets bigger the lower you get down.
30:51To resist that higher pressure lower down, the river wall itself needs to get wider and more massive to stay
30:57stable under the water pressure.
31:00Behind me, you can see the shape which tapers upwards.
31:04Today, dams all over the world use this same taper design.
31:08It has kept the Houses of Parliament standing tall in the river for over 160 years.
31:15But these stones aren't invincible.
31:18On the rooftop, the stonework is under attack.
31:22On the Lord's roof, architect Adam Wotropski investigates the fabric of the building.
31:29There's a gargoyle up there with a head missing.
31:32The stone corroded so much that that head probably fell off.
31:36Engineers must constantly monitor Parliament's limestone exterior.
31:39This black is an accumulation of atmospheric pollution produced by coal fires and by factories during the Victorian era.
31:48This pollution will have long-term effects on the building.
31:52The pollution that you see on the surface is quite damaging because the rain falls on it and the black,
31:58which is carbon, forms acid.
32:01And the acid then changes the composition of the stone into this powder, which just simply drops off.
32:09Adam's team must replace this deteriorated stonework with new, more robust limestone.
32:15A job that continues across the building.
32:18But pollution is not the only thing that threatens Parliament's delicate stone.
32:24There is one ever-present danger that only Parliament's most unusual team can tackle.
32:32I do get a lot of funny looks, especially when people pass me.
32:35A lot of the time they look back at me because I don't believe what they've just seen.
32:50Mark Bigwood and his hawk angel protect Parliament from a surprising threat.
32:56London's army of pigeons.
33:00Angel's job is to keep the pigeons off the building.
33:03Pigeon's droppings are very acidic to the limestone that the palace is built of.
33:08And it would cause an awful lot of damage to the stonework.
33:11Some are very irreversible.
33:13Without this essential work, the pigeon droppings could destroy the palace's delicate limestone facade.
33:22The aim isn't to actually catch the pigeons.
33:26Angel's presence here provides all of the deterrent needed.
33:29Pigeons are naturally afraid of birds of prey.
33:33And pigeons recognize the fact that he's a bird of prey so they are afraid of it.
33:37Mark and Angel's rooftop patrols have had a huge impact.
33:41When we started working here about 10, 15 years ago, there was approximately 30, 40 pigeons that were permanently on
33:51site.
33:52They were roosting and nesting on site.
33:53And now there's just a couple of pigeons that wander in during the day.
33:59Mark and Angel's invaluable work is helping to keep Parliament's stonework pristine.
34:05160 years after it was built.
34:09Today, investigators are unlocking the secrets held inside this extraordinary building.
34:17They're finding spaces that appear to have hidden purposes.
34:22Could this vast cavity at the heart of the building be the secret to understanding these huge tunnel systems?
34:37London's Houses of Parliament.
34:40A Victorian engineering marvel encased in a spectacular Gothic shell.
34:47Parliament isn't just a monument.
34:49It's a living, working building.
34:54The Victorians had to make sure people could work here during the coldest winter months.
35:01Open fires heated up its 1,000 plus rooms.
35:07So how did they stop Parliament from filling up with smoke?
35:13An amazing innovation sits right at the heart of the palace.
35:17This elaborate spire is, in fact, a chimney that sits above the palace's busy central lobby.
35:25Warm air from the room below rose up through a hole in its domed roof.
35:30This created an upwards current that pushes smoke up and out of the gigantic spire through 16 holes spread across
35:39the tower and 32 open windows.
35:46This hidden ventilation system was the first of its kind anywhere in the world.
36:00Today, this chimney is locked up and kept secret from most visitors to Parliament.
36:15Architect Adam Watrobski investigates if it could really have worked as the designers hoped.
36:21We're directly over central lobby, which is the crossroads of the Palace of Westminster.
36:26This location is crucial to the Victorian chimney design.
36:31Adam wants to test just how efficient the ventilation system was.
36:35You can feel really quite a strong updraft coming from central lobby below me here.
36:41I've got this piece of kit here, which, as I step back, will measure the airspeed.
36:46It's very rapidly rising here, quite a high speed.
36:51This air current is strong enough to push smoke up and out of the spire.
36:55It's even faster than modern air conditioning systems.
36:58This part of the historical ventilation system would have really worked quite well.
37:05Clean air flowed in through the tops of the tallest towers to avoid the pollution of the city.
37:12Giant 10-foot fans drew fresh air through huge tunnels in the basement and pumped it to hundreds of rooms
37:20across the palace.
37:22Below the House of Commons, a gauze filter purified the air.
37:26A water spray moistened it and hot coils made it warm before releasing it into the chamber.
37:34Old air rushed out through the ceilings and funneled through the spire.
37:38Here, the air rising from the central lobby lifted it from the building.
37:46Today, the huge heating and ventilation tunnels in the building have been repurposed and are equipped with modern utilities.
37:54But Adam still finds traces of this pioneering system throughout the building.
38:03This is one of the original ventilation hatches which were controlled by an army of people in these underground tunnels.
38:10And this was used to allow the fresh air into the tunnels and to be subsequently warmed and distributed throughout
38:16the building.
38:19This ventilation system evolved as time and technology progressed, sometimes involving some bizarre gadgets.
38:28Well, this is the periscope which was incorporated in the post-war reconstruction of the House of Commons.
38:36This piece of submarine technology had a unique use.
38:40And if you look through it, you can see quite clearly what's happening in there.
38:46I can see the speaker's chair and I can see the benches at the side.
38:52Whoever sat here would be able to control the building's air conditioning.
38:56The idea of a periscope is a fabulous idea.
39:00So that whoever was controlling the air conditioning system in here could actually see live what was happening straight away
39:05before the advent of closed circuit television.
39:10Today, the periscope is no longer in use.
39:15Ingenious engineering enabled Parliament's residents to stay warm and provided them with fresh air to breathe.
39:22The finishing touch was to make the Houses of Parliament beautiful.
39:27It is Britain's most prestigious building and the Victorians insisted it be spectacular inside and out.
39:41In the central lobby, stonemason Andy Midwinter is making sure it stays that way.
39:48We're doing exactly the same as what the Victorians did.
39:53The stained glass windows, wood carvings and statues must all be looked after.
39:59But with over one million people passing through Parliament every year, it's the Gothic floor tiles that need the most
40:06attention.
40:08Originally, when they were first laid, they'd be quite a vibrant colour.
40:11Over the years, basically the pattern starts erasing.
40:18Andy must carefully cut every single tile out of the floor.
40:23We use a little tile cutter with a nice thin blade.
40:29So what we literally do, cut between the two tiles.
40:32So we release the pressure around the sides of the tiles.
40:37And then we'll just get a hammer and a claw and gently put it underneath the tile.
40:44And give a couple of taps and the tiles should gently lift without damage.
40:49His next job is to replace each original tile with an exact replica.
40:54This is a brand new tile which has been made specifically for this floor.
41:00The design is exactly the same as the original Pugin design.
41:05Right down to like the little dots, the colours, everything.
41:10Recreating these Victorian tiles hasn't been easy.
41:14The original manufacturers don't exist no more.
41:18A modern manufacturer had to reproduce these tiles one by one, matching the patterns by eye.
41:24It's been a slow process.
41:26It has been about six years in the making.
41:29They are handmade.
41:31Even the very simple sort of tiles, it still takes skill.
41:35It's an art form in itself.
41:37And these modern replacements even improve on the Victorian models.
41:42They are fired at a much higher temperature than the originals would have been.
41:47It makes the tile a much, much harder tile.
41:51All that's left is to lay them in the floor.
41:54It's a huge job.
41:56The tiles cover an area the size of a football field.
42:00On average, one panel, I think it's 714 tiles.
42:08And we've done 10 panels, 12 panels.
42:11I would say it myself, over 5,000 tiles.
42:16And we've got many, many more to go.
42:19When Andy is finished, the splendor of the Victorian's vision will shine through again.
42:30Thanks to a dedicated team of experts working across the building, this aging mega palace can expect to grow old
42:38gracefully and survive hundreds of years into the future.
42:44It's remarkable roof, high-precision clock, and unique ventilation system.
42:53All evidence of a building light years ahead of its time.
42:58A true masterpiece of the Victorian age.
43:02And one of the most awe-inspiring buildings ever created.
43:18The End
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