0:00:05 > 0:00:11Something new is happening on Planet Earth, big enough to be seen from space.
0:00:13 > 0:00:18Hot spots buzzing with the energy of millions of people.
0:00:19 > 0:00:22For the first time in human history,
0:00:22 > 0:00:26more of us live in cities than in the country.
0:00:26 > 0:00:30But these are cities on a different scale.
0:00:31 > 0:00:35In just 50 years, we've seen the birth, the growth
0:00:35 > 0:00:39and now the dominance of the megacity.
0:00:43 > 0:00:46Sprawling, seething, noisy,
0:00:46 > 0:00:49polluted, crammed with 10 million,
0:00:49 > 0:00:5315, sometimes even 30 million people.
0:00:53 > 0:00:58These cities are complicated, fragile places,
0:00:58 > 0:01:00constantly on the edge.
0:01:02 > 0:01:06These are places overcrowded in squalor.
0:01:07 > 0:01:12But these are also the most exciting places on the Earth...
0:01:13 > 0:01:16..brimming with optimism and fun and energy.
0:01:16 > 0:01:19Wahey! Arrgh!
0:01:19 > 0:01:23Love them or loathe them, fear them or embrace them,
0:01:23 > 0:01:28the megacities are the human future of the planet.
0:01:29 > 0:01:34'They are also Man's biggest and most dangerous social experiment yet.
0:01:39 > 0:01:44'How do you begin to protect and control a city
0:01:44 > 0:01:46'of 20 million people?
0:01:49 > 0:01:55'I've been off to look and learn, going to an evasive driving school on the edge of Mexico City
0:01:55 > 0:02:02'where kidnapping is a huge social problem, not just for the rich, but for the middle classes too.
0:02:03 > 0:02:10'I've signed up as a rather wrinkled volunteer in London's Police Riot Control Academy.'
0:02:10 > 0:02:16There's nothing quite like being hailed with bricks and petrol bombs to make you see things differently.
0:02:16 > 0:02:23'And I've been disaster training in Tokyo, the world's most advanced metropolis.'
0:02:24 > 0:02:27This is, um...not funny.
0:02:42 > 0:02:46So far, our planet has 21 megacities,
0:02:46 > 0:02:49home to at least ten million people each.
0:02:49 > 0:02:55Every one of them struggles with unprecedented problems of crime and social control.
0:02:56 > 0:02:59Not new, but new in scale.
0:02:59 > 0:03:06And these great cities are peculiarly vulnerable to natural threats as well.
0:03:06 > 0:03:11Why is this? It's because from Ancient Rome's Pompeii under its volcano
0:03:11 > 0:03:14to San Francisco on its fault line,
0:03:14 > 0:03:20many of mankind's greatest cities have grown where they did not because of human stupidity,
0:03:20 > 0:03:25but because fault lines produce rich, natural soil
0:03:25 > 0:03:29and vulnerable bays are very handy for trade.
0:03:31 > 0:03:33Take Tokyo -
0:03:33 > 0:03:39two major rivers running through it and built on fabulously mineral-rich land,
0:03:39 > 0:03:42which is why it is where it is,
0:03:42 > 0:03:45but this natural richness is no accident.
0:03:45 > 0:03:48It comes from underground.
0:03:48 > 0:03:53Tokyo's 33 million residents are living right on top of three
0:03:53 > 0:03:57of the world's most unstable geological fault lines.
0:03:59 > 0:04:01Or Dhaka,
0:04:01 > 0:04:05a haphazard, unregulated city, built on a fertile flood plain.
0:04:05 > 0:04:09Great farming, great fishing, which is why it's there.
0:04:09 > 0:04:15But in consequence, its 13 million people now face catastrophic flooding,
0:04:15 > 0:04:17rising sea levels and disease.
0:04:25 > 0:04:30London, not only one of the oldest megacities, but the only one in Europe
0:04:30 > 0:04:36and then only if we take in all of its suburbs, is well protected from the sea with a hi-tech barrier.
0:04:36 > 0:04:40But as a global city, one of the world's most mixed metropolises,
0:04:40 > 0:04:45its 13 million people are particularly vulnerable to terrorist attack.
0:04:49 > 0:04:53My journey, however, begins in Mexico City,
0:04:53 > 0:04:56home to more than 20 million people
0:04:56 > 0:05:00and a city built on an ancient, now hidden lake...
0:05:02 > 0:05:08..surrounded by mountains, prone to severe earthquakes and flooding,
0:05:08 > 0:05:13but most urgently drowning under a tidal wave of crime.
0:05:14 > 0:05:18Almost everywhere has got some kind of problem with crime.
0:05:18 > 0:05:22But in Mexico City, it's at a different level.
0:05:22 > 0:05:26Large, extremely violent drug gangs.
0:05:26 > 0:05:31Trafficking, prostitution and kidnapping.
0:05:31 > 0:05:34According to one local crime survey,
0:05:34 > 0:05:40there are something like 500 kidnaps in Mexico every month.
0:05:40 > 0:05:45In fact, Mexico is the kidnap capital of the world.
0:05:45 > 0:05:48And it's not just the rich who are targets.
0:05:48 > 0:05:52Kidnappers will go for anyone they think has got a bank account
0:05:52 > 0:05:55or for their children or grandmother.
0:05:55 > 0:06:02In this city, they snatch at cash points, in the middle of traffic even, in taxis.
0:06:02 > 0:06:06Why is this? Partly because of the example of the drug cartels.
0:06:06 > 0:06:11Partly because the millions in poverty live jammed up against the better off,
0:06:11 > 0:06:14their noses rubbed in middle-class success.
0:06:17 > 0:06:22Something which is obvious when you see the city from above.
0:06:28 > 0:06:31From your perspective, literally up here,
0:06:31 > 0:06:37things like kidnapping, is that because there's so many rich and so many poor very close together?
0:06:37 > 0:06:42- It's definitely due to the contrast. - Yeah.- The contrast in social classes.
0:06:42 > 0:06:47You can see from one hill to the other huge economic differences.
0:06:47 > 0:06:51In an area where you'll find on one hill one house,
0:06:51 > 0:06:55on the other one you'll find 40 or 50 families living.
0:06:56 > 0:07:01'It isn't just the super wealthy who are living in DIY fortresses.
0:07:01 > 0:07:07'Even in the lower middle class suburbs, residents have built their own gated communities
0:07:07 > 0:07:12'and paid for their own armed guards to protect themselves against thieves and kidnappers.
0:07:12 > 0:07:17'Throw in a police force with an ineffective and often corrupt reputation
0:07:17 > 0:07:22'and it isn't hard to see why Mexico City's crime rate is out of control.
0:07:24 > 0:07:28'Around here it seems it's often pointless to call the police,
0:07:28 > 0:07:32'but there are people who are willing to help for a price.
0:07:36 > 0:07:41'Tom Cseh is a former United States Air Force Special Agent.
0:07:42 > 0:07:46'But he's become Mexico City's self-styled kidnap guru.'
0:07:46 > 0:07:52Here in the Mexico City area, 80% of kidnaps happen in the morning
0:07:52 > 0:07:56when the victim is on their way from their residence to work or to school.
0:07:56 > 0:08:01Why is that? Because most of us follow some sort of routine in the morning.
0:08:01 > 0:08:05The bad guys do not go after the very well-to-do
0:08:05 > 0:08:10who mostly have their own security, either armoured cars or bodyguards or whatever.
0:08:12 > 0:08:17'Tom's most over-subscribed service is his evasive driving course.
0:08:17 > 0:08:24'He regularly teaches Mexico City's middle-class mums how to beat kidnappers at their own game.
0:08:24 > 0:08:28'Can he, however, do the same for an ageing British hack
0:08:28 > 0:08:33'who has no ambitions to be Jeremy Clarkson? Lesson number one...'
0:08:33 > 0:08:39You're driving down the road and maybe some bad individuals pull up alongside of you.
0:08:39 > 0:08:42They will tell you "pull over" in Spanish. You hit the brake.
0:08:42 > 0:08:45They're going to drive on at least a car length.
0:08:45 > 0:08:51You're going to come to a complete stop and make a U-turn. It's a very safe manoeuvre.
0:08:51 > 0:08:55'A very safe manoeuvre? Well, up to a point.
0:08:55 > 0:09:03'Now, I am an impatient driver, but this is not quite my normal style outside the local supermarket.
0:09:05 > 0:09:09'The 180-degree, gangster-avoiding handbrake turn!'
0:09:09 > 0:09:11God!
0:09:11 > 0:09:13SHOUTING
0:09:22 > 0:09:28'Now, that didn't seem too bad, but I'm not finished yet. Now Tom wants me to go on to the attack.'
0:09:28 > 0:09:33OK, the next manoeuvre is what we call "the surgical" or "the PIT and turn".
0:09:33 > 0:09:39This is very commonly used by US police departments in the United States to stop a fleeing felon.
0:09:39 > 0:09:44This is also useful in Mexico because if the bad guys pull up alongside of you,
0:09:44 > 0:09:49you know exactly where you need to hit that car to knock them off the road.
0:09:49 > 0:09:52I'll learn how to knock people off the road?
0:09:53 > 0:09:59- They're going to pull up, threaten us.- OK.- And then you're going to hit them.
0:09:59 > 0:10:04It's that area right between the rear tyre and the rear fender.
0:10:06 > 0:10:09TYRES SCREECH
0:10:13 > 0:10:16- CLATTER - Sorry!- You're all right.- Yeah.
0:10:16 > 0:10:18Sorry.
0:10:18 > 0:10:22Now, wait a minute. Don't film that! LAUGHTER
0:10:23 > 0:10:26'And Tom's got one more lesson for me.'
0:10:26 > 0:10:31OK, so this is your typical blocked highway here.
0:10:31 > 0:10:36The bad guys are blocking you. You're coming down a one-way street. You cannot reverse out.
0:10:36 > 0:10:39The only option is to go forward and if you want...
0:10:39 > 0:10:44- This kind of thing happens in Mexico City?- It happens in Mexico City, yes.- OK.
0:10:44 > 0:10:49So the bad guys would never expect that you are going to ram their car.
0:10:49 > 0:10:54'Yet driving into another car proves surprisingly difficult.
0:10:54 > 0:10:57'Even in London, it's not exactly instinctive.'
0:10:57 > 0:10:59SHOUTING
0:11:01 > 0:11:03Oh... 'Missed!'
0:11:03 > 0:11:06Sorry.
0:11:08 > 0:11:10'Take two.'
0:11:10 > 0:11:13Esta es la calle de Morelos!
0:11:16 > 0:11:18Good. Right on.
0:11:20 > 0:11:22That was worryingly enjoyable.
0:11:24 > 0:11:26- Thanks, bad guys! - LAUGHTER
0:11:32 > 0:11:38Most of Mexico City's kidnappers are, of course, simply desperate opportunists.
0:11:38 > 0:11:42The alienating, unfair and cramped atmosphere of the megacity
0:11:42 > 0:11:45encourages some very violent individuals.
0:11:46 > 0:11:51But what happens when parts of the megacity kick off en masse?
0:11:54 > 0:11:58Cities are places where millions of people are crammed together
0:11:58 > 0:12:04and sometimes they are places where millions of very angry people are crammed together
0:12:04 > 0:12:08and it doesn't take much to light the touchpaper.
0:12:10 > 0:12:12CHANTING
0:12:12 > 0:12:18When a riot does kick off, streets turn from shopping arcades and open-air cafes
0:12:18 > 0:12:23into narrow, high-stakes battlefields and it happens the world over.
0:12:29 > 0:12:32- Go! - ALL: Ten, nine, eight, seven, six,
0:12:32 > 0:12:35five, four, three, two, one!
0:12:41 > 0:12:47'So every self-respecting megacity needs to have a defence force on stand-by
0:12:47 > 0:12:51'and I'm reporting for basic training with London's.
0:12:51 > 0:12:57'These men aren't crack troops. They're ordinary bobbies from the London Metropolitan Police Force.'
0:12:57 > 0:13:00Five, four, three, two, one!
0:13:03 > 0:13:08'Yet all the kit that's needed to combat a riot in a metropolis
0:13:08 > 0:13:11'quickly turns these perfectly pleasant bobbies and me
0:13:11 > 0:13:15'into what could be seen as faceless storm troopers.'
0:13:15 > 0:13:19I've always wanted to look well built. This is the cheating way.
0:13:19 > 0:13:24- And you'll be feeling quite warm now. - I'm already feeling hot, yeah.
0:13:24 > 0:13:26God, it's a formidable outfit.
0:13:26 > 0:13:29Three, two, one, go!
0:13:31 > 0:13:35'The suits are fire-proof, sweat-proof and knife-proof.
0:13:35 > 0:13:41'The stab vest alone weighs about eight kilos, so they're not the easiest things to get around in
0:13:41 > 0:13:46'and that's without the added weight of a nine-kilogram polycarbonate shield.'
0:13:46 > 0:13:49Come on, keep going, keep going!
0:13:49 > 0:13:51I thought I was quite fit.
0:13:51 > 0:13:54But that was hard.
0:13:55 > 0:13:57It's the weight of all this stuff.
0:13:57 > 0:14:02'Next we're taught how to treat an ordinary street as a war zone.'
0:14:02 > 0:14:05- 902, forward!- Forward!
0:14:06 > 0:14:10'I feel a bit like I've been thrown back in time.'
0:14:13 > 0:14:19What really strikes me about this is we have a very, very sophisticated, modern city here,
0:14:19 > 0:14:24and all these megacities, these huge metropolises are sophisticated and modern,
0:14:24 > 0:14:30and in the end, we are behaving just in the same way that Julius Caesar's troops behaved.
0:14:30 > 0:14:34Short shields back, short shields back!
0:14:34 > 0:14:38It's exactly the same tactics you'll read from 2,000 years ago.
0:14:38 > 0:14:42- Go! - With long shields linking and short shields moving forward and back.
0:14:42 > 0:14:46- Short shields, let's head for the rear.- Head for the rear.
0:14:47 > 0:14:53'In the modern megacity riot, though, it's not arrows and spears you need protection against.
0:14:53 > 0:14:57'As darkness falls, the training is stepped up
0:14:57 > 0:15:01'and more realistic riot conditions take over.
0:15:01 > 0:15:04'We're up against an ugly, angry mob.
0:15:04 > 0:15:11'They're actually off-duty coppers playing at being fascist or anarchist thugs.
0:15:11 > 0:15:14'They're taking the game seriously enough.
0:15:24 > 0:15:30'In a riot, the familiar, everyday fabric of the city takes on a different look.
0:15:30 > 0:15:36'Paving slabs and bottles and bricks and waste bins become weapons.'
0:15:39 > 0:15:43REPORTER: Dozens of police and demonstrators were hurt by missiles
0:15:43 > 0:15:47including bottles, stones and scaffolding poles.
0:15:47 > 0:15:49Cars were overturned and set alight.
0:15:51 > 0:15:55'Riots are caused by all sorts of different factors -
0:15:55 > 0:15:59'oppressive politics or racial tension, religious extremism.
0:15:59 > 0:16:04'But some scientists have discovered what they think is another rather simpler trigger -
0:16:04 > 0:16:06'heat.
0:16:06 > 0:16:11'An increase in temperature causes a higher serotonin release in the brain
0:16:11 > 0:16:15'which in turn leads to increased aggression.
0:16:18 > 0:16:21'So here's a rather bizarre claim.
0:16:21 > 0:16:26'27 to 32 degrees Centigrade is apparently optimum rioting weather.
0:16:36 > 0:16:40'Back at my riot and apparently, we're winning.
0:16:40 > 0:16:45'After taking a battering and absorbing everything they can unleash on us,
0:16:45 > 0:16:49'we can advance and bring the crowd under control.'
0:16:51 > 0:16:57There's nothing quite like being hailed with bricks and petrol bombs to make you see things differently.
0:16:57 > 0:17:03My admiration for these guys is pretty high just at the moment, but you'd expect that.
0:17:03 > 0:17:06It's just the petrol talking.
0:17:10 > 0:17:12Escucha! Jesucristo...
0:17:12 > 0:17:17'Back in Mexico City, it isn't just the police force that needs to be kitted out.
0:17:19 > 0:17:27'This is an exceptionally dangerous city where it pays to wear the right thing at the wrong end of a gun.
0:17:29 > 0:17:34'Miguel Caballero, named after its owner, is a stylish boutique
0:17:34 > 0:17:40'selling a rather special line in men's clothing for the Mexico City gent about town.'
0:17:41 > 0:17:45This is like an ordinary fashion collection.
0:17:45 > 0:17:47- That is the idea.- There you go.
0:17:47 > 0:17:51Now we have a shirt, now we have tops.
0:17:51 > 0:17:57- That is all the sweaters. - Nice jerseys.- That is totally new. It's from last week.
0:17:57 > 0:18:03- The only thing different about them is that they'll stop you being gunned down?- Yeah.- That's amazing.
0:18:03 > 0:18:07We have to guarantee discretion, fashion, comfort.
0:18:07 > 0:18:10- These are the guns you protect against?- Yeah.- Wow!
0:18:10 > 0:18:14- That is high protection. - These are serious machine guns.
0:18:14 > 0:18:21'Made of reinforced Kevlar, the exact composition of Miguel's bullet-proof clothing is a secret.'
0:18:21 > 0:18:27What kind of people are coming in for this? What kind of people are asking for it?
0:18:27 > 0:18:30- Politicians.- Politicians, yeah, obviously.- CEOs.
0:18:31 > 0:18:36CEOs of the companies, president of the companies.
0:18:37 > 0:18:43- Gobernadors.- Yeah. Basically, rich people who think they're targets?- Yeah.
0:18:43 > 0:18:45- Can I try on this?- Totally.
0:18:45 > 0:18:48Yeah, that's a bit more, um...
0:18:48 > 0:18:54for an evening out. You're taking someone out and you think you might be machine-gunned, so you wear...
0:18:54 > 0:19:00If you are on any weekend and you want to maintain the casual wear, that is the perfect idea.
0:19:00 > 0:19:02Yeah, it's big protection.
0:19:02 > 0:19:05Let's have a little look in the mirror.
0:19:05 > 0:19:11- The idea is all the time to maintain your discretion.- You wouldn't know I was bullet-proof protected.
0:19:11 > 0:19:13So how much would this cost me?
0:19:13 > 0:19:17It's around 900 US dollars to 4,900 US dollars.
0:19:20 > 0:19:24'Strange fact - Mexico City has just got one legal gun shop.
0:19:24 > 0:19:29'100 miles away, though, over the border with the United States, there are 7,000 of them.
0:19:29 > 0:19:34'You don't need to be an economic genius to work out what's going on. Poor old Mexico.
0:19:34 > 0:19:39'Miguel is showing me just how much protection his casual wear offers.'
0:19:39 > 0:19:42We're now here at the police shooting range.
0:19:42 > 0:19:44And I've got the jacket.
0:19:44 > 0:19:51However, I've been told that BBC Health & Safety won't allow ME to be actually shot,
0:19:51 > 0:19:57so I'd like to say sorry to those people watching who were desperate to see Andrew Marr take one.
0:19:57 > 0:20:02'However, Oscar, one of Miguel's employees, has kindly agreed to take one on my behalf.'
0:20:02 > 0:20:08And then we're going to go through into the shooting range and you'll see what happens next.
0:20:08 > 0:20:11We'll all see what happens next.
0:20:11 > 0:20:13- Let's go through.- Please.
0:20:15 > 0:20:17So here's the gun.
0:20:17 > 0:20:20Now, one bullet. One bullet only.
0:20:20 > 0:20:24We always give the opportunity to the victim to choose the bullet.
0:20:24 > 0:20:28You want to choose the bullet? OK. This is gruesome.
0:20:28 > 0:20:31There's your bullet. All right, mate.
0:20:46 > 0:20:48Uno!
0:20:48 > 0:20:50GUNSHOT
0:20:52 > 0:20:54Wow!
0:20:55 > 0:20:59- Are you all right?- Yeah. - You feel OK?- Yeah.
0:20:59 > 0:21:02Nothing there. God!
0:21:02 > 0:21:04And there it is.
0:21:04 > 0:21:06That's amazing.
0:21:06 > 0:21:08- It's hot.- It's hot.
0:21:08 > 0:21:11Oh, it's hot, yeah. Still hot.
0:21:12 > 0:21:16- And you're not in pain? It's not sore?- No, nothing.
0:21:16 > 0:21:22Wow! I think I need one of these. Next time I'm in Downing Street, I'll take one of these with me.
0:21:22 > 0:21:25- If you want, I can shoot you? - That, not this.
0:21:26 > 0:21:32But who do you turn to if you are one of the millions of metropolis denizens
0:21:32 > 0:21:38who doesn't have a thousand dollars for a special kind of jacket?
0:21:38 > 0:21:44Tepito is one of the toughest, most down-at-heel areas of Mexico City.
0:21:44 > 0:21:48Here, criminals and victims and their friends and families
0:21:48 > 0:21:51have turned to an altogether different type of protection.
0:21:51 > 0:21:56She is big, she's popular and she goes by the name of Santa Muerte,
0:21:56 > 0:21:58or Saint Death.
0:22:00 > 0:22:07What people say about Santa Muerte is that she is there for the people at the bottom -
0:22:07 > 0:22:11the hard guys, people who have done terrible things and their victims.
0:22:11 > 0:22:14There's an official Catholic shrine just 20 yards away.
0:22:14 > 0:22:18It's been extended, it's a kind of rival "come and look at me" shrine
0:22:18 > 0:22:22on behalf of the Catholic Church who hate this stuff.
0:22:22 > 0:22:25It's bigger, it's more impressive.
0:22:25 > 0:22:27And there's nobody there.
0:22:27 > 0:22:35Dona Queta, known locally as the Queen of Tepito, has made caring for the shrine her life's work.
0:22:37 > 0:22:40TRANSLATOR: This is very important for a mother like her,
0:22:40 > 0:22:47for a mother like a lot of mothers that have maybe a kid in the jail or a kid that is doing drugs.
0:22:47 > 0:22:49And they are concerned.
0:22:49 > 0:22:54They want to put their faith in something, somebody that is going to help them.
0:22:54 > 0:23:00It's also for people that are going to lose their houses and they need money for the rent.
0:23:00 > 0:23:06They don't have money and they don't see how they are going to get it. They come and make their praise.
0:23:06 > 0:23:08It's hope for everybody.
0:23:08 > 0:23:14Why are people leaving cigarettes? And what else are they leaving? There's sweets and fruit and...
0:23:14 > 0:23:17DONA QUETA SPEAKS IN SPANISH
0:23:17 > 0:23:22TRANSLATOR: It's an offering. You put food, you put cigarettes.
0:23:22 > 0:23:25They bring this stuff every day.
0:23:25 > 0:23:29At lunchtime, people will bring more food, and dinnertime, the same.
0:23:29 > 0:23:33- Basically, what you like the best is what you would offer.- I see.
0:23:33 > 0:23:35I get it.
0:23:35 > 0:23:38'This man, who doesn't want to appear on telly,
0:23:38 > 0:23:43'has worshipped Santa Muerte for ten years and he swears by her.'
0:23:44 > 0:23:48I've just been told that his brother had been kidnapped
0:23:48 > 0:23:52and day after day, he'd come here and pray to Santa Muerte,
0:23:52 > 0:23:55begging her to get his brother freed.
0:23:55 > 0:23:58And not only was his brother freed,
0:23:58 > 0:24:04his brother was freed at the moment the senior kidnapper was himself murdered.
0:24:04 > 0:24:11And not only that, the kidnapper's body was brought past the family house on the way to be buried.
0:24:11 > 0:24:15And that, he said, is what Santa Muerte can do.
0:24:20 > 0:24:25Mexico City - where you wear a bullet-proof jacket to the corner shop,
0:24:25 > 0:24:30where mothers and murderers worship at the shrine of Saint Death.
0:24:30 > 0:24:34So what on earth do people do for fun here?
0:24:34 > 0:24:38Well, it seems that that can be pretty violent as well.
0:24:43 > 0:24:46On any given night of the week,
0:24:46 > 0:24:5050,000 Mexicans flock to the city's ten huge arenas
0:24:50 > 0:24:54to lose themselves in their favourite sport.
0:24:57 > 0:25:02My guides tonight are die-hard fans Alejandro and Francisco.
0:25:02 > 0:25:06We're here for the "lucha libre" or "free wrestling",
0:25:06 > 0:25:11which is half recognisable sport and half nightmarish pantomime.
0:25:11 > 0:25:14And it seems the crowd can't get enough of it.
0:25:14 > 0:25:17MUSIC: "We Will Rock You"
0:25:27 > 0:25:30For the residents of Mexico City,
0:25:30 > 0:25:35watching 250-pound men pile-drive each other into the floor
0:25:35 > 0:25:39seems to be perfect therapy after an average day in the megacity.
0:25:44 > 0:25:49- Do the crowd get almost as aggressive as the ring? - Yeah, that's correct.
0:25:49 > 0:25:54Most of the people use the sport to yell, to take out all of the stress of the...
0:25:54 > 0:25:57- Get all their emotions out.- Yeah.
0:25:57 > 0:26:03There's a lot of craziness in the city, so you come out here to scream, to shout, to throw beer.
0:26:03 > 0:26:07- Because of the craziness in the city, it's a release?- Yeah.
0:26:09 > 0:26:11CHEERING
0:26:11 > 0:26:16'With good guys and bad guys to cheer and to boo...'
0:26:16 > 0:26:17Boo!
0:26:17 > 0:26:22'..I'm again reminded of life in one of the first great metropolises.'
0:26:25 > 0:26:30We've always loved a bit of communal violence - human beings.
0:26:30 > 0:26:35And around me here people are using the same gestures
0:26:35 > 0:26:39that they used to use when they were watching the gladiators
0:26:39 > 0:26:43or the Christians being eaten by lions in Ancient Rome.
0:26:46 > 0:26:49'Well, the Royal Ballet it ain't.
0:26:49 > 0:26:55'But the atmosphere is certainly infectious. It's raw, loud, unzipped,
0:26:55 > 0:26:58'somewhere between pantomime and sumo.
0:26:58 > 0:27:03'And over the course of the evening, I can see why it is so popular.'
0:27:04 > 0:27:08No-one's being hurt here tonight, I think.
0:27:08 > 0:27:11But these are really important events
0:27:11 > 0:27:15because they allow people to let off steam.
0:27:15 > 0:27:17They're like kettles.
0:27:17 > 0:27:21And the more stress there is out in the city,
0:27:21 > 0:27:23the louder the whistle.
0:27:23 > 0:27:26JEERING
0:27:35 > 0:27:39If the residents of Mexico City flock to arenas
0:27:39 > 0:27:42to vent their pent-up frustrations,
0:27:42 > 0:27:46on the other side of the world, in Tokyo,
0:27:46 > 0:27:51one small band has decided to turn the megacity itself into a giant arena.
0:27:56 > 0:28:00To be more accurate, an extraordinary, vast race track.
0:28:02 > 0:28:07After a lot of persuasion, they've agreed to meet us at a secret rendezvous point
0:28:07 > 0:28:10somewhere off Tokyo's main airport highway.
0:28:13 > 0:28:18Well, every Saturday, me and my friends get together.
0:28:18 > 0:28:24We run the highway, you know, who's fastest. Not really a race, but yeah, a race.
0:28:24 > 0:28:26TYRES SCREECH
0:28:28 > 0:28:30Meet the Hashiriya...
0:28:32 > 0:28:37..Tokyo's street racers who regularly risk life and limb
0:28:37 > 0:28:43to drive at ludicrous speeds through Tokyo's state-of-the-art megacity road network.
0:28:46 > 0:28:50Here, you can do anything, touge, you know, up mountains
0:28:50 > 0:28:52and do the winding stuff.
0:28:52 > 0:28:56You can go towards the ocean and do drifting.
0:28:56 > 0:29:01You can go to Shuto Expressway, you can do circuit roads and stuff like that.
0:29:01 > 0:29:08During the week, these guys have ordinary jobs. They go to work. They toe the line.
0:29:08 > 0:29:10They're model citizens.
0:29:12 > 0:29:17But come Saturday night, the Hashiriya tear up Tokyo's rulebook.
0:29:17 > 0:29:21All that matters is driving as fast as you possibly can.
0:29:23 > 0:29:26You can go 200mph for 300km.
0:29:29 > 0:29:33The fastest I've been is, like, 320, 323.
0:29:33 > 0:29:36Some of the guys have run 340.
0:29:36 > 0:29:43'It's a deadly game, obviously, but for these Tokyo men it's one way of escaping the daily pressures
0:29:43 > 0:29:45'of life in the metropolis.'
0:29:45 > 0:29:49You feel free. You get out all this stress and stuff.
0:29:49 > 0:29:52All these people, all this crowd.
0:29:59 > 0:30:06A few boy racers letting off steam and breaking the rules isn't going to threaten the mighty metropolis.
0:30:08 > 0:30:12But we can never afford to underestimate the level of damage
0:30:12 > 0:30:17a few single-minded individuals are capable of unleashing.
0:30:22 > 0:30:27Over the past 10 years, the work of a handful of suicidal terrorists
0:30:27 > 0:30:32in cities like Mumbai, Madrid, London
0:30:32 > 0:30:35and, of course, New York have sent shock waves around the world
0:30:35 > 0:30:42and the message for the future of the megacities is now the bleak one - be prepared.
0:30:53 > 0:30:59We're told that London, like many other megacities, is still a prime terrorist target
0:30:59 > 0:31:03and we're told it's not a question of if the attack happens, but when.
0:31:03 > 0:31:10So if, God forbid, you are caught up in such an attack and the world goes dark
0:31:10 > 0:31:15and the buildings around you collapse and you're left, trapped,
0:31:15 > 0:31:17who do you turn to?
0:31:17 > 0:31:21Well, you turn to the specially-trained men and women
0:31:21 > 0:31:27who are waiting all round the clock, all round the year, for that phone call.
0:31:30 > 0:31:37This is the Urban Search and Rescue Unit, one of more than 21 specialist teams dotted around the UK
0:31:37 > 0:31:42which were set up in direct response to the 9/11 attacks and the threat of more.
0:31:42 > 0:31:48These two key members of the team are Darcy and Lucy. With two years' training under the collar,
0:31:48 > 0:31:54they're sent into the rubble of collapsed buildings to sniff out survivors.
0:31:54 > 0:31:59It is dangerous work and the dogs have to wear protective boots
0:31:59 > 0:32:02as they scramble over the inhospitable landscape.
0:32:04 > 0:32:09If there is a dead body in the wreckage, they're trained to ignore it.
0:32:09 > 0:32:13That grisly task falls to a different dog team.
0:32:16 > 0:32:22'So what do you do if someone's trapped in an air pocket under 50 tonnes of concrete?
0:32:22 > 0:32:24'Using a specialist drill,
0:32:26 > 0:32:32'the team has to first bore into the concrete to make a hole big enough for them to insert
0:32:32 > 0:32:34'a high-tech camera.'
0:32:38 > 0:32:40You get a good colour picture.
0:32:40 > 0:32:47We can see that no one is just the other side of this wall. We can now demolish this quickly.
0:32:47 > 0:32:50- Speed is of the essence.- Absolutely.
0:32:50 > 0:32:54'There's a good reason why they use reinforced concrete in buildings -
0:32:54 > 0:33:00'it's tough, it's very tough. I think this might shake my fillings out.
0:33:00 > 0:33:05'It can take hours, even days working around the clock to knock through.'
0:33:05 > 0:33:10- We need to break all that out. - That's physically quite hard work.
0:33:10 > 0:33:16'Even when the teams break into the buildings, there's often more concrete to smash through
0:33:16 > 0:33:21'before the dogs can pinpoint the exact location of the bodies.'
0:33:21 > 0:33:25I'm just going to do something, mate, to make it easier.
0:33:26 > 0:33:31'Dirty, cold and grim as the work might be, it's comforting to know
0:33:31 > 0:33:35'that this team at least are prepared for the unthinkable.'
0:33:35 > 0:33:41As the cities get bigger and more complicated and the threats become greater,
0:33:41 > 0:33:45so the response has to be cleverer, too.
0:33:45 > 0:33:50A few years ago, places like this didn't exist.
0:33:50 > 0:33:55And yet, although it is a sophisticated and thought-through response to the next attack,
0:33:55 > 0:34:02the next collapse of a building, at one level it's also reassuringly basic.
0:34:02 > 0:34:09In the end, it's down to smell and muscle and a certain amount of courage.
0:34:18 > 0:34:23But the human damage that can be inflicted is only one side of it.
0:34:23 > 0:34:28All around the world, we're constantly reminded about the devastation
0:34:28 > 0:34:34that can be wreaked on the most modern-seeming city by good old-fashioned nature.
0:34:36 > 0:34:39Earthquakes. Floods.
0:34:39 > 0:34:45Typhoons. By choosing to build on some of the Earth's most geographically unstable locations,
0:34:45 > 0:34:53the metropolises are at times more exposed to the extremes of nature than less populated parts.
0:34:53 > 0:34:59When they chose to settle near coastlines, waterways and fertile river valleys -
0:34:59 > 0:35:05important for a city's survival - our ancestors could never have known they were laying their foundations
0:35:05 > 0:35:08on slow, but remorseless time bombs.
0:35:18 > 0:35:22More than half the world's 21 megacities of 10 million people
0:35:22 > 0:35:26are in positions that leave them vulnerable to earthquakes.
0:35:32 > 0:35:37And most at risk of all of them is Tokyo,
0:35:37 > 0:35:42which lies on a complex and menacing web of geographical fault lines.
0:35:42 > 0:35:50Scientists have told us the chances of a major earthquake not hitting Tokyo at some point were zero.
0:35:50 > 0:35:53And they've been proved chillingly right.
0:35:53 > 0:35:59The epicentre of the recent Sendai earthquake was hundreds of miles from the city centre,
0:35:59 > 0:36:05but it was a devastating Scale 9 and the resulting tsunami wreaked apocalyptic havoc
0:36:05 > 0:36:11on the immediate areas, killing more than 18,000 people. Many people are still missing.
0:36:11 > 0:36:16And Tokyo didn't escape as powerful aftershock tremors hit the city.
0:36:16 > 0:36:23So in the face of this onslaught, just how prepared was the most advanced, most efficient metropolis?
0:36:23 > 0:36:26SPEAKS IN JAPANESE
0:36:26 > 0:36:33Regular earthquake practice drills required by every Tokyo school were suddenly a reality.
0:36:35 > 0:36:40Thousands of schoolchildren were safely evacuated to open ground.
0:36:40 > 0:36:46'So focused are the people of Tokyo on arming themselves against the forces of nature,
0:36:46 > 0:36:50'they've set up so-called life learning centres around the city
0:36:50 > 0:36:57'where residents can experience pretty much every extreme that nature's likely to throw at them,
0:36:57 > 0:37:03'from the typhoons which dump down thousands of gallons of rain water in Japan every year
0:37:03 > 0:37:06'to the full force of an earthquake.
0:37:06 > 0:37:14'This robotic platform is designed to mimic all the different magnitude levels an earthquake can unleash.'
0:37:14 > 0:37:18- Hold.- Hold onto this. - ..Protect your head.
0:37:18 > 0:37:22- Turn the gas off, right. - Please open the door.
0:37:22 > 0:37:26'I filmed this some months before the Sendai earthquake
0:37:26 > 0:37:31'and the aftershock of a magnitude of 6.4, which was felt in Tokyo.'
0:37:32 > 0:37:36This is going to be number seven. See what happens.
0:37:40 > 0:37:44And it really is shaking quite a lot!
0:37:44 > 0:37:47And I'm underneath...underneath...
0:37:47 > 0:37:49Ah! Bloody hell!
0:37:49 > 0:37:51It's quite something! Oh!
0:37:53 > 0:37:56This is more than a tremor.
0:37:56 > 0:37:59This is quite scary.
0:37:59 > 0:38:01Jesus Christ!
0:38:01 > 0:38:04This is...not funny. At all.
0:38:13 > 0:38:15And it's stopped.
0:38:15 > 0:38:18I crawl out... My goodness me.
0:38:18 > 0:38:22Cupboards have fallen down. Off with the gas.
0:38:22 > 0:38:26Check that door. Is it going to open?
0:38:26 > 0:38:28Thank goodness. Yes, it is.
0:38:28 > 0:38:30If this was for real,
0:38:30 > 0:38:38in a city of 30 million people, I'm on the ground floor, one person with some padded furniture.
0:38:38 > 0:38:42And the shock has been... I'm still actually moving.
0:38:42 > 0:38:46You know, inside my head. It's really quite something.
0:38:46 > 0:38:49It's like being seasick or very drunk.
0:38:49 > 0:38:57Just imagine what would happen to 30 million people, many of them many floors up. Absolutely terrifying.
0:38:59 > 0:39:01Well, as we know, it did happen.
0:39:01 > 0:39:07However, Tokyo has nearly 3,000 really high buildings - more than 30 storeys.
0:39:07 > 0:39:13Every single one is built to survive a high-level earthquake. That is impressive engineering.
0:39:13 > 0:39:16And it largely worked.
0:39:16 > 0:39:20Despite the strength of the tremors that shook buildings to their core,
0:39:20 > 0:39:26there was relatively little structural damage and just 7 deaths in the city itself.
0:39:28 > 0:39:35The earthquake threat to this densely-built megacity is so great, the response is on a huge scale.
0:39:37 > 0:39:43This is the city's Disaster Management Centre which is, of course, earthquake-proof.
0:39:43 > 0:39:47Totally self-contained, it's got its own independent power supply
0:39:47 > 0:39:52and communications to the outside world.
0:39:52 > 0:39:56And this is the man at the heart of the operation, Mr Toshiyuki Shikata,
0:39:56 > 0:39:59Tokyo's Security Counsellor.
0:39:59 > 0:40:05This is where the people who run the metropolis come to implement their highly-planned response.
0:40:06 > 0:40:11All the information that we need we can see.
0:40:11 > 0:40:17On the centre screen sometimes I have a conversation with the Prime Minister.
0:40:18 > 0:40:24Vast amounts of supplies are stockpiled. This time, luckily, they weren't needed.
0:40:26 > 0:40:30Cans, pickles, 4.09 million.
0:40:30 > 0:40:34And blankets, 890,000.
0:40:34 > 0:40:40So the authorities in Tokyo, indeed the authorities in Japan, were pretty well prepared,
0:40:40 > 0:40:47but the earthquake showed just how quickly a highly modern infrastructure can collapse
0:40:47 > 0:40:53because it took 10 days before the authorities finally got supplies like these
0:40:53 > 0:40:59flowing into the disaster zones. The stakes are very high as this death meter in Tokyo shows.
0:41:00 > 0:41:02We estimate
0:41:02 > 0:41:077.3 as it hit... on this point.
0:41:07 > 0:41:09In that case, it is...
0:41:09 > 0:41:15almost 6,400 people will be killed.
0:41:16 > 0:41:21As we discovered, an earthquake can be far more lethal than that,
0:41:21 > 0:41:28but again Tokyo is, perhaps, the best prepared city in Japan and probably in the world.
0:41:28 > 0:41:32At the heart of the megacity's survival masterplan
0:41:32 > 0:41:37is a building which dwarfs the entire city.
0:41:37 > 0:41:39Still under construction,
0:41:40 > 0:41:44the Sky Tree is 634 metres high,
0:41:44 > 0:41:48currently the second-tallest structure in the world.
0:41:50 > 0:41:54If, or rather when, a disaster strikes again,
0:41:54 > 0:42:00this broadcasting tower will be crucial to keeping communications running.
0:42:00 > 0:42:04But how do you build a tower two-thirds of a kilometre high
0:42:04 > 0:42:10which is strong enough to stand up to the most powerful earthquakes?
0:42:10 > 0:42:14Engineers looked to Japan's past and they've rather ingeniously borrowed
0:42:14 > 0:42:20from a tradition that goes back 1,000 years - pagoda temple architecture.
0:42:20 > 0:42:22Just like the temples,
0:42:22 > 0:42:27the Sky Tree is built out of two independent elements.
0:42:27 > 0:42:31In the Sky Tree's case, there's a central concrete shaft
0:42:31 > 0:42:38and a surrounding steel structure. And when an earthquake hits the building, both move separately,
0:42:38 > 0:42:41in theory, cancelling each other out.
0:42:42 > 0:42:47And in practice because when the massive aftershock struck Tokyo,
0:42:47 > 0:42:50this anti-seismic design did prove itself.
0:42:50 > 0:42:56There was no damage to the structure of the building at all and the 500 people working on it were uninjured.
0:42:56 > 0:43:01Tokyo's planning and super technology helped them be prepared.
0:43:01 > 0:43:05This time, it survived the worst of the immediate effects of the earthquake.
0:43:05 > 0:43:12But the full power of nature means that the world's most advanced metropolis still faces
0:43:12 > 0:43:14an unpredictable future.
0:43:20 > 0:43:27If you live in one of the poorer megacities and disaster strikes, the odds aren't strongly in your favour.
0:43:30 > 0:43:37On the other side of the planet, just like Tokyo, Mexico City's land has become its enemy.
0:43:40 > 0:43:45Sitting in a massive geographical bowl, surrounded by mountains and volcanoes,
0:43:45 > 0:43:49and built on a network of tributaries from an ancient lake,
0:43:49 > 0:43:54it's vulnerable to both earthquakes and, more crucially, flooding.
0:43:56 > 0:44:02More than seven million people occupy the shanty towns that sprawl across the hillsides.
0:44:03 > 0:44:08Most are haphazardly constructed without proper foundations.
0:44:08 > 0:44:15Factor in the endless building work that's cleared and concreted over vital tree and vegetation cover
0:44:15 > 0:44:19and you have a very dangerous place to be living in.
0:44:23 > 0:44:28It's the 30th October, 2009, in the middle of the afternoon.
0:44:28 > 0:44:34It's the end of a month which has seen the highest rainfall here since records began.
0:44:34 > 0:44:38And over the next three or four hours,
0:44:38 > 0:44:43a downfall of biblical proportions takes place.
0:45:01 > 0:45:07This is one part of the city, like so much of it, which is completely unplanned and absolutely crammed.
0:45:07 > 0:45:13Migrant families simply arrive here, search around for a little scrap of land they can call their own
0:45:13 > 0:45:17and start to build a house with their own hands.
0:45:18 > 0:45:25Now as a result, when the flood comes, thousands and thousands of houses are swept away.
0:45:25 > 0:45:31The Jimenez family built their house here, on the edge of the creek.
0:45:32 > 0:45:34And, as you can see, it's gone.
0:45:34 > 0:45:41'The Jimenez family have since built themselves another house, but it's a precarious existence
0:45:41 > 0:45:44'and the threat of flooding is never far away.'
0:45:44 > 0:45:48Could you ask them how high the water came?
0:45:49 > 0:45:54SHE TRANSLATES: One metre and 20 centimetres. Where you see the mark.
0:45:54 > 0:45:57How did they all get out?
0:45:58 > 0:46:04They climbed that wall and then the next wall and after that there's a school
0:46:04 > 0:46:10where they found shelter. All the water came in this direction and they needed to get out.
0:46:13 > 0:46:18We are living through a time of more and more extreme weather conditions
0:46:18 > 0:46:23and when that kind of stress hits, it hits megacities first
0:46:23 > 0:46:29and it seems to hit the poorest first because they're the people in the most fragile parts.
0:46:29 > 0:46:31That's exactly what's happened here.
0:46:32 > 0:46:38There's an annual rainfall of more than 27 inches in Mexico City. Quite a lot.
0:46:38 > 0:46:43'And yet, rather oddly, this city has never got to grips with dealing with so much water.
0:46:43 > 0:46:48'And the problem lies right here in the network of underground drains.'
0:46:49 > 0:46:51Amazing.
0:46:51 > 0:46:53- Fantastic, no?- Yeah.
0:46:53 > 0:46:56Underground river.
0:46:56 > 0:47:01So when the rains come, how high up does the water go?
0:47:01 > 0:47:05- It fills the full pipe. - It fills the pipe.
0:47:05 > 0:47:10- What's the water coming down? Just the drain?- The overflow of the lake.
0:47:10 > 0:47:13Oh, I see. OK.
0:47:13 > 0:47:19'The system goes right back to the 18th century, way before Mexico City's population exploded.
0:47:19 > 0:47:23'It was designed to capture fresh rain water from the floods,
0:47:23 > 0:47:25'but now it can't cope.'
0:47:25 > 0:47:32This is mostly sewage coming down from the city where about a million people live.
0:47:32 > 0:47:35- A million people's sewage?- Yes.
0:47:35 > 0:47:40'Water expert Valente Souza is trying to solve the contamination problem.'
0:47:40 > 0:47:47You see, Andrew, this line is the last of this... of this rainy season's level.
0:47:47 > 0:47:51- It comes all the way... - Above us.- Exactly.
0:47:51 > 0:47:55At this very point. And we walk 150 feet down
0:47:55 > 0:48:01into another collector that drains the rainfall and now the sewage.
0:48:01 > 0:48:07- We don't have our masks now, but it smells... The methane is strong.- Really bad.
0:48:07 > 0:48:13- And this is water...- Rainfall. - That could be used by the city of Mexico.- Absolutely.
0:48:13 > 0:48:15If they did things more sensibly.
0:48:17 > 0:48:21'It really is a case of water, water everywhere, but not a lot to drink.
0:48:21 > 0:48:26'Mexico City's hidden underground system is old and buckling
0:48:26 > 0:48:31'and, frankly, failing to keep pace with its rapid growth.'
0:48:38 > 0:48:43But let's go back to the megacity whose technological know-how
0:48:43 > 0:48:48does appear more than up to these natural struggles.
0:48:49 > 0:48:53'Built to protect against major typhoon flooding,
0:48:53 > 0:48:59'this extraordinary underground drain complex lies 50 metres below the surface
0:48:59 > 0:49:01'on the outskirts of Tokyo.
0:49:01 > 0:49:04'And it's taken more than 18 years to build.
0:49:17 > 0:49:19'Five giant concrete silos,
0:49:19 > 0:49:21'65 metres high,
0:49:21 > 0:49:27'are connected to pumps powerful enough to shift 200 tonnes of water every second.
0:49:28 > 0:49:33'And the whole subterranean system spans almost four miles.
0:49:36 > 0:49:38'It is a thing of wonder.'
0:49:41 > 0:49:46I think if the pharaohs of Ancient Egypt had built cathedrals,
0:49:46 > 0:49:50this is sort of what they would have come up with.
0:49:50 > 0:49:54But it's an interesting commentary on the modern city.
0:49:54 > 0:50:00This isn't about religion or the spiritual or the worship of great men.
0:50:00 > 0:50:04This is...civil engineering.
0:50:05 > 0:50:10Just what we have to do to keep the show on the road.
0:50:16 > 0:50:213,000 miles away, the megacity of Dhaka in Bangladesh
0:50:21 > 0:50:27is in another world compared to Tokyo's mighty technological planning.
0:50:33 > 0:50:38'A lot of Dhaka lies just a few metres above sea level.'
0:50:40 > 0:50:47When the annual monsoons hit the city, it's swamped by more than six feet of rain.
0:50:48 > 0:50:54If sea levels rise as much as some scientists say they will,
0:50:54 > 0:50:58there's a real chance the entire city will have to be evacuated.
0:50:58 > 0:51:00Where would these people go?
0:51:00 > 0:51:07And when you consider that 85% of its 13 million population lives in slum conditions,
0:51:07 > 0:51:10without proper drainage,
0:51:10 > 0:51:14where a single toilet may be shared by as many as 400 people,
0:51:14 > 0:51:19then Dhaka, quite obviously, faces another huge ongoing problem.
0:51:19 > 0:51:21'Disease.'
0:51:21 > 0:51:23Well, here they are.
0:51:23 > 0:51:26This is, uh, a toilet.
0:51:27 > 0:51:31It's very straightforward. You do your business here.
0:51:31 > 0:51:36Actually, this is quite a posh toilet for a slum.
0:51:36 > 0:51:40But the important thing is what happens next.
0:51:40 > 0:51:42If you come here...
0:51:44 > 0:51:50The human sewage, the crap, goes directly down there, underneath the toilet,
0:51:50 > 0:51:55and joins the rest of it, and as the water rises
0:51:55 > 0:51:59the sewage goes back into the water system.
0:51:59 > 0:52:04And if you wonder what kills most urban people,
0:52:04 > 0:52:09it isn't starvation, it's not even natural disaster.
0:52:09 > 0:52:12It's crap in the water system.
0:52:14 > 0:52:20Dhaka's constantly waterlogged state means it's impossible to keep dirty and clean water separate.
0:52:20 > 0:52:25A single gram of human faeces can contain ten million viruses and a million bacteria
0:52:25 > 0:52:30with far-reaching consequences for many of us.
0:52:31 > 0:52:33Among other things,
0:52:33 > 0:52:39the crammed and dirty slums of the megacities are the perfect breeding ground
0:52:39 > 0:52:42for the next global pandemic.
0:52:42 > 0:52:47Right at the start it will seem like nothing at all.
0:52:47 > 0:52:51A cough. A child sneezing in a shack over there.
0:52:51 > 0:52:57But it could be the beginning of a catastrophe that affects you,
0:52:57 > 0:53:00me, everyone we know.
0:53:08 > 0:53:14'There's no high-tech solution here. The answers lie with individuals like Runa Khan,
0:53:14 > 0:53:20'a charity worker who is fighting an endless battle to keep Dhaka's slums free of disease.'
0:53:22 > 0:53:25Epidemics are a big problem in the slums.
0:53:25 > 0:53:2910 members of the family living in one little room.
0:53:29 > 0:53:33There are no toilets, no drinking water. If you see the river,
0:53:33 > 0:53:37this is the primary source of drinking water and bathing water.
0:53:37 > 0:53:43You put your fingers in, you come out with six fingers. It's one of the most polluted rivers in the world.
0:53:46 > 0:53:50Here, there is a prevalence of healthcare, there are hospitals,
0:53:50 > 0:53:56but the sheer number and volume of people inhibits the population from accessing this healthcare.
0:54:03 > 0:54:08'Today Runa's visiting a patient who's been ill for quite some time.'
0:54:16 > 0:54:22'The infection spread in the slum is a lot more dramatic than in other parts of the country.
0:54:22 > 0:54:27'It's very difficult to predict or to take care of.
0:54:29 > 0:54:36'Luckily, this turns out to be a bug which can be treated and contained, but any one of these cases
0:54:36 > 0:54:42'could turn out to be the start of an epidemic that reaches far beyond Dhaka, even around the world.
0:54:42 > 0:54:46'You start seeing two cases, five cases, ten cases.
0:54:46 > 0:54:52'And in a place where you have more than 2,000 people per square kilometre, you are scared
0:54:52 > 0:54:55'because it can't be controlled.
0:54:55 > 0:55:02'This is a very big challenge, not only for small organisations like us, but the government itself.'
0:55:06 > 0:55:12The outbreak of the next global pandemic poses a very real, very urgent threat
0:55:12 > 0:55:14to all the world's metropolises.
0:55:15 > 0:55:20The sheer size and frequency of world air traffic
0:55:20 > 0:55:25creates a perfect storm for the spread of global disease.
0:55:25 > 0:55:29There are more than 35,000 air routes around the world,
0:55:29 > 0:55:35and every year one and a half billion people are carried on 40 million flights.
0:55:35 > 0:55:40Air travel is turning the planet into one giant metropolis.
0:55:44 > 0:55:51It looks like a pretty ordinary office, but this is the United Kingdom's first line of defence
0:55:51 > 0:55:54against the outbreak of deadly diseases.
0:55:54 > 0:56:00The Health Protection Agency has teams of scientists on a state of constant alert.
0:56:00 > 0:56:08They're part of a worldwide network. Professor Maria Zambon is Director of the Centre for Infections.
0:56:08 > 0:56:13Diseases never sleep. It is like very fine-grained detective work
0:56:13 > 0:56:18where not only are you piecing together different pieces of information,
0:56:18 > 0:56:21you're also tracking things.
0:56:21 > 0:56:27Bugs and germs can evolve very quickly and scientists are trying to prevent the next super disease
0:56:27 > 0:56:29taking us all by surprise.
0:56:29 > 0:56:34A nine-to-five day doesn't do it. You need to work round the clock
0:56:34 > 0:56:38to develop the data to make sure that you have the answers.
0:56:39 > 0:56:44The solutions don't end with boffins in laboratories.
0:56:44 > 0:56:47Dealing with our next global epidemic takes huge resources.
0:56:47 > 0:56:55Stockpiles of vaccines in huge secret warehouses are just one of the things that it takes
0:56:55 > 0:57:00to keep our world of megacities from disaster.
0:57:05 > 0:57:09'So terrorism, rioting,
0:57:09 > 0:57:12'kidnap, earthquake,
0:57:12 > 0:57:14'floods
0:57:14 > 0:57:18'and plague - it's not an entirely cheerful outlook.
0:57:18 > 0:57:21'It might even be called doom-laden.
0:57:22 > 0:57:24'However...'
0:57:24 > 0:57:30as we've seen, some excellent science, superb engineering and simple forethought
0:57:30 > 0:57:33does mean we've developed defences.
0:57:34 > 0:57:38Death and taxes remain inevitable.
0:57:38 > 0:57:40Catastrophe doesn't.
0:57:41 > 0:57:46Life in the megacities is dangerous and exciting,
0:57:46 > 0:57:49but then it always has been.
0:57:54 > 0:58:00'Next time I'm going to be finding out how transport has shaped the metropolis.'
0:58:00 > 0:58:03Oh, my God! Oh, I'm sorry.
0:58:03 > 0:58:07That was both...great fun and really, really hard work.
0:58:07 > 0:58:11'I'll ask if there are different ways of feeding the hungry cities.'
0:58:11 > 0:58:14This makes me feel...gaseous.
0:58:14 > 0:58:17And horrible. Just look at this!
0:58:19 > 0:58:25And I'll meet the smelly heroes dealing with all the stuff metropolises don't want.'
0:58:26 > 0:58:29Unimaginable, what he's lowered himself into.
0:58:40 > 0:58:44Subtitles by Subtext for Red Bee Media Ltd - 2011
0:58:45 > 0:58:47Email subtitling@bbc.co.uk