NARRATOR: No place on the planet has shaped the world quite like this one. And this bustling, self-confident city. has an extraordinary story to tell. SIMON: London is an archaeological gold mine. NARRATOR: London's secret ingredient, the mighty River Thames. Where its deepest and darkest mysteries lie waiting to be found. Imagine if we could empty the oceans. Letting the water drain away. To reveal the secrets of the sea floor. Now we can. Using accurate data and astonishing technology, to bring light once again to a lost world.

Why is this one of the most dangerous shipwrecks in the world? Can these century old remains cast light on London's pirate past? ERIC: The Queen and her major advisors, they were all tied up in this violent trade. NARRATOR: And how did London's favorite warship explode into 1,000 pieces? (theme music plays).

Rich with history and tradition. Today, London is a global center of tourism, fashion, music and commerce. Home to more than eight million people, famous for their eccentricity. And attitude. And it all starts with fast flowing water. SIMON: The River Thames is absolutely vital to the story of London, without the River Thames there would be no London. NARRATOR: For thousands of years people have lived along the banks of the Thames. But how does the City of London begin? Could some extraordinary ruins hold the answer?

As new buildings rise they expose evidence of the past. On the north bank of the River Thames, in the heart of the financial district, workers digging new foundations unearth something surprising. They call in the experts. The lead archaeologist is Gustav Milne. GUSTAV: Before the new buildings went up, a series of archaeological excavations took place here, and they revealed some amazing discoveries. NARRATOR: When Gustav's team arrives only part of the remains are exposed. GUSTAV: Archaeological excavations are a bit like crime scene investigations, we like to tape off the area to stop people trampling over it,

and we like to record all sorts of information, which at the time might not seem relevant. NARRATOR: The best way to see this remarkable find is to drain away the city. The London pavement cracks. Soft, alluvial soil begins to crumble away. Based on highly accurate archaeological data, we can peer below the modern city. And witness the origins of London. Huge wooden timbers, clearly part of something very big and very old.

GUSTAV: We can count the tree rings, this is a system called dendrochronology, you have to slice them up by chainsaw, and then look at the distance between each of the rings and match that to a master chronology. NARRATOR: These trees are chopped down almost 2,000 years ago, a time when something very important happened in southern England. The arrival of a super power. ANDREW: The Romans came to Britain to asset strip, they plundered its rich resources, and they were going to use it to sustain the rest of their empire.

NARRATOR: The Romans come looking for riches. But what they find is trouble. SIMON: Roman Britain was the wild west of the Roman empire. NARRATOR: The Roman army builds an imposing settlement on the River Thames. And they call it Londinium. The giant timbers are unique evidence of this moment. GUSTAV: There is no surviving documentary record that tells us when London was founded, we rely entirely on archaeological evidence to build up the real story of Londinium.

NARRATOR: Removing even more of the modern city other clues emerge. The timbers are part of a 7 foot high wall. Behind it, the remains of Roman buildings. GUSTAV: Those buildings were not residential buildings, they didn't have mosaic floors or hearths in.

NARRATOR: So what are these structures for? Clues lie in bore samples taken from soil next to the timber wall. VIRGIL: We found things like ostracods, which are millimeter sized crustaceans, and diatoms, which are single celled algae remains. NARRATOR: Many of these creatures thrive in tidal estuaries, but, the archaeological site is over 300 feet from the modern estuary river. The explanation, in Roman times the Thames was much wider and ran right alongside this timber wall. GUSTAV: If only you could remove all these buildings, drain the River Thames, you would get a perfect view of what we found.

NARRATOR: The wall is a Roman quayside, almost 200 feet long. Set alongside ten stone buildings. Gustav's team hasn't just found some ancient pieces of wood, they've discovered the site of the city's first major harbor facility. Now it's possible to recreate the first port of London as it looked in the late first century AD.

On its north bank, The Thames floods back to its ancient, original width. And Londinium rises from the tidal mud. Cargo ships from all over the known world unload along the wooden quayside. Along ten large stone warehouses. Where goods are stored and processed. SIMON: Roman London is an emporium, it's a place of trade, and therefore the port is absolutely vital. NARRATOR: The port gives London power and importance. A place to live and defend. It transforms a simple, river settlement into a thriving town.

ANDREW: We often get obsessed about Roman temples and amphitheaters, but actually, building a port is the thing that really makes Britain work. NARRATOR: But for London to become the dominant Roman city of Britain it needs something else. Close to the dock, archaeologists unearth more game changing evidence that's been hidden for centuries. The drained site reveals what they found. Part of a 20 foot rectangular wooden box. GUSTAV: The timbers were felled in about 85 AD or thereabouts.

NARRATOR: The new structure is also Roman. And around the same age as the dock. But what is it? Gustav turns to other archaeological evidence found nearby. NARRATOR: Remnants of Roman roads right across London. One runs close to the wooden box and stops dead at the river's northern bank. Another does the same on the southern bank. Solid proof of a river crossing. But not by boat. GUSTAV: We think that the timber structure was a pier base for a Roman bridge.

NARRATOR: Now, using all of the latest research, we can run the clock backwards and highlight the crowning glory of Roman London. The first ever permanent Thames crossing stretches for over 12,000 feet. The 20 foot wide superstructure is supported by 20 massive timber piers, with bases like the one found by Gustav's team. There's nothing else like it in Roman Britain. It's an ancient engineering marvel.

A marvel that rises from the ashes of war. In 60 AD, Queen Boadicea and her powerful tribe rebel against Roman rule. And burn London to the ground. After finally defeating her in battle the Romans rebuilt their city. SIMON: So, London becomes the provincial capital because London is the place where all the rebuilding starts for Roman Britain. NARRATOR: The bridge is a key part of this rebuilding program, sending a message about the enduring power of Rome. SIMON: This is monumentalization on a huge scale for the Romans, saying we are here, we're controlling this river crossing,

this is our provincial capital. NARRATOR: Incredibly, it's the city's only bridge for almost 1,000 years. It's what ties London and the rest of Roman Britain together. Cementing London's place as the centerpiece of the country and, along with the nearby port, kick starting the city's remarkable growth. 1400 years later and London is still going strong. Its success now fueled by violent, swashbuckling adventurers. Can some mysterious remains in the Thames estuary expose one of its darkest secrets?

NARRATOR: Just as in Roman times, the modern river Thames is London's transport artery. Today, the heavyweight shipping action happens 20 miles out of town in the Thames Estuary. Every year, giant vessels carry 50 million tons of cargo through these dangerously shallow, tidal waters. CAPTAIN: And we're now outbound for Sea Reach 4. NARRATOR: The Thames is patrolled by the Port of London Authority. Or PLA. Monitoring the ever-changing river bed to keep shipping channels clear. In 2003, a PLA survey vessel discovers a mysterious object in the busy Prince's Channel.

JOHN: What we're looking at here is an area in the Prince's Channel, which we're going to dredge. We'd surveyed it, we'd found something that didn't look quite right, and that's this relatively small obstruction. NARRATOR: Further sonar scans reveal it's a shipwreck. JOHN: These are manmade structures we're looking up here, and they turned out to be the ribs of a ship. That's when it all got very exciting and that's when all the follow up investigations started to happen. NARRATOR: The PLA calls in archaeologist Jens Auer. JENS: Everything was mysterious in the beginning, unknown wreck, where is it from?

What could it be? What did it carry? I can remember my first dive very well. Couldn't see very much and it looked extremely confusing, there were timbers everywhere and bits of metal everywhere. And because of the strong currents things are moving around constantly. NARRATOR: Despite the challenging conditions, Jens immediately knows that the wreck is very old. But what is it? And why is it here?

The poor visibility and fast currents make it difficult to get the full picture. But now, using dive survey data and powerful computer software. we can make the Thames Estuary drain away. And expose a remarkable sight. As the murky waters recede. part buried in shifting sands, an 80 foot skeleton. Floor timbers and adjoining frames remain. To an expert its design gives clues to its age. JENS: This type of construction, this joining of the frames and some other features in the construction, the little details, they sort of pointed to the 16th century.

NARRATOR: In the 16th century England is ruled by ruthless Tudor monarchs. Under their command, London's wealth and global ambition skyrockets. The mystery wreck is a chance to learn more about this dramatic age, so Jens wants to identify it. Between the ship's timbers he finds some striking clues. Tin, lead ingots and iron bars. It's carrying a small fortune in metal.

JENS: The cargo told us we were looking at a merchant vessel. NARRATOR: But exploring the drained wreck further reveals this is no ordinary trading ship. In the nearby sand, cannons, engraved on one of the guns, the initials TG, and the symbol of a grasshopper. JENS: Did some research and found out that TG stands for Thomas Gresham, Sir Thomas Gresham. NARRATOR: Sir Thomas Gresham is a key figure in 16th century London, one of the men who first turn England into a global power house.

ERIC: Thomas Gresham was one of the greatest financiers of his day. He was an entrepreneur and a very successful one at that. NARRATOR: In 1566, Gresham establishes England's first purpose built trading center, called The Royal Exchange. It's such an important moment for the country that it's opened by Queen Elizabeth herself. Studying the wreck in greater detail reveals something astonishing. Gun ports.

NARRATOR: The merchant vessel isn't trading cannon, it's armed with them. Now using Jens' forensic research, we can dial back time and restore this relic of Elizabethan London to her former glory. Rising from her resting place, a state of the art 16th century merchantman. 115 feet long.

Weighing 200 tons. Carrying over a dozen cannon. An ocean going trader from a time when England is making its presence felt on the world stage. JENS: Ships were the most advanced means of transporting and of communicating, you could compare it to a rocket nowadays. NARRATOR: But why does a merchant ship need so many guns? The answer exposes the brutal truth that lies behind London's rise to power.

NARRATOR: Identifying the 16th century mystery wreck might explain why it's armed. Investigator Jens Auer, asks archaeologist Gustav Milne, for help. GUSTAV: We have got a little bit of litigation which we found. NARRATOR: In 1603, a similar sized vessel sinks, just outside London in the Prince's Channel. GUSTAV: And the name of the ship is the Cherubim, it was what we call a Levanter. That is to say a merchantman which sailed to Turkey and back with the Levant Company.

NARRATOR: The Cherubim isn't owned by Thomas Gresham. But there is a connection. The Levant Company uses cannon from Gresham's Iron Foundry. But why would it need them? GUSTAV: It wasn't just a Levanter, it was a privateer. JENS: A privateer. GUSTAV: Or pirate, whatever you wanna call it, yeah. In 1591 it joined the Azores Campaign to attack, with its guns, Spanish galleons coming back from the Caribbean with bullion in it. NARRATOR: Like other English vessels of her time, the Cherubim is also a part time pirate ship.

Targeting England's enemies and looting their treasure. ERIC: The world had first been conquered by the Spanish and the Portuguese, which, towards the end of the 16th century came together in a single empire. So, if England wanted to play a part in this increasingly global trade she had to play catch up. She had to raid the empires that already existed. The Queen and her major advisors, the Lord Admiral, they were all tied up in this violent trade.

NARRATOR: Some of the most famous English sea captains are also part time pirates. Or, to use the politer phrase, Sea Dogs. ERIC: When Francis Drake sailed around the world he made a profit for his investors, including the Queen, of 4,700%. You're talking about the equivalent really of billions of pounds by modern standards. This was big money indeed. And the fruits of piracy were very good. NARRATOR: By the late 16th century, between 10 and 15% of all the goods brought into the Port of London are the result of privateering.

Making the city, the crown and merchants, like Thomas Gresham, filthy rich. But the Cherubim's buccaneering adventures come to a sudden end in 1603. Leaving London, heavy with a valuable cargo, she is caught in a storm in the Thames Estuary and disappears from view for centuries. Fast forward 60 years, London is a center of world trade and opportunity, its population swelling from 200,000 to 350,000.

The era of state piracy is over. And now it's England's turn to be the target of greedy rival powers. To protect her merchants the Royal Navy must expand, fast. Can these shattered remains explain how Britannia came to rule the waves? In 2005, a Port of London survey ship is scanning the riverbed. When its sonar picks up something big. MAN: Just coming up to it now, Paul.

There's the wreck. NARRATOR: The remains are 40 miles from London, in the Thames Estuary. Archaeologist Alison James, and diver Steve Ellis investigate. Their job is to find out whether the site is historically important. ALISON: We're taking the clues that we find, in this case on the seabed, because we're working underwater, and using it to build up a picture of the wreck, so, every single clue could be very significant.

NARRATOR: They use a side scan sonar to gather more information. STEVE: This is the data that's coming from the tow fish. It's just like one massive underwater jigsaw puzzle. And it's just a challenge, I love it. MAN: Okay, diver into water. ALISON: It takes a certain type of diver to want to dive in the Thames. Visibility is fairly poor, it's highly tidal, and the location of the vessel does make it a challenging environment to dive.

NARRATOR: First, giant timbers come into view. Then something intriguing. NARRATOR: Along with cannonballs, personal belongings litter the sea bed. A sailor's clay pipe. A navigational divider. There's evidence everywhere. The best way to make sense of this underwater jigsaw puzzle is to see all the pieces clearly.

As the estuary water pours away, the carcass of an old wooden ship emerges into the light once again. A 65 foot section of the hull lies semi buried in silt. It was once a large vessel. But now it's in pieces. Inside the main section of the hull. shoes, books, and a sundial compass, all signs that passengers and crew had little time to escape. Back on shore, specialists try to ID the wreck by analyzing relics pulled from the river bed. Ramrods, cannonballs. All examined in forensic detail.

One of the most crucial pieces of evidence, leather shoes. ANGELA: We have a large number of shoes which are of a very similar construction and style. And they are very typical for the 17th century. ALISON: It's incredibly special to be able to find a 17th century vessel lying on the sea bed in this country. NARRATOR: And records reveal that one heavily armed warship did sink in these waters in the 17th century, and, appropriately, she's called The London. ALISON: The London is the only candidate of the right size and scale and period that's in the vicinity.

NARRATOR: In the mid-17th century, England's rulers invest heavily in the Navy to protect trade. ERIC: If England was going to be a great power it had to be a naval power. NARRATOR: Calling one of England's latest warships The London is a symbol of the city's ever-growing influence. ANDREW: The London is a heavyweight bruiser, it's gonna go forward and it's gonna smash the enemy. NARRATOR: So, how did such a heavyweight champion end up at the bottom of the estuary? The drained wreck reveals a clue.

The ship is in pieces. One fragment and some cannon lie 1300 feet from the main body of the wreck. The vessel has been ripped apart. ALISON: It is really clear that a catastrophic event has occurred. NARRATOR: So catastrophic that the ship's plight is recorded in one of the most famous diaries of the age, written by the Secretary to the Admiralty, Samuel Pepys. PEPYS: This morning is brought me to the office the sad news of The London, in which Sir Joe Lawson's men were all bringing her from Chatham to The Hope, and thence she suddenly blew up. About 24 men and a woman that were in the Roundhouse and

Coach saved, the rest, being above 300, drowned. NARRATOR: But in friendly waters, what could have caused such a devastating explosion? NARRATOR: In the mid-17th century England and Holland are at war. The London is preparing for a battle in the English Channel when it suddenly blows up. Archaeologists want to know why. Clues lie inside the wreck. Buried in one small section, a gunner's kit. Breaching ropes to reduce recoil, hand spikes to move the cannon, and lint stocks to help fire the guns.

But the equipment is not located near the gun stations, where it would be on a ship ready for battle. ALISON: We'd expect to find a hand spike, a lint stock, by every cannon effectively, but that's not what we're seeing, we're seeing everything in one very small area. NARRATOR: One possibility is that the items are still in storage. ALISON: We found all of these things in a relatively small area, possibly the gunner's store, but it clearly shows the ship was not ready for war. NARRATOR: With the help of historical records it's possible now to dial back the centuries and reveal the anatomy of a disaster.

ALISON: The London was making its way up to The Hope from Chatham where it would have taken on board senior officers ready to set sail and take part in the war. NARRATOR: With the leaders due on board shortly the crew urgently prepare the ship. ALISON: This is a very busy ship getting ready to go to war, with large amounts of gunpowder on board and a huge hive of activity. NARRATOR: No-one knows what, but something causes a fire. ALISON: It's very cramped conditions, the men are working in deck areas with very low ceilings, it would have been lit by candles, they may have been smoking.

NARRATOR: The fire quickly spreads to the magazine. Packed with 12 tons of gunpowder. After The London disaster, the Royal Navy standardizes tactics, procedures and equipment to try and improve safety. ALISON: Because of accidents like The London, they started to introduce tests to have more professional officers, so you really start to see the Navy changing after the loss of The London. NARRATOR: The Royal Navy evolves into one of the greatest military forces ever to go to sea. And it's this maritime strength that allows Britain to build a vast empire.

London continues to grow. Spectacularly. By 1840, 2 million people live in the city, making it the biggest and most powerful in the world. Throughout the 19th and early 20th centuries, Britain's power draws her into numerous conflicts. Some very close to home. One and a half miles off the coast of Kent is a rusting hulk that still threatens London today.

Naval architect, Dr. Nick Bradbeer, has spent his life studying ships. But he's never been face to face with one as deadly as this. NICK: Right now I'm out in the Thames Estuary, and just over there we can see the three masts still above the waves. These buoys mark the edge of the exclusion zone, inside which boats are not allowed to enter. NARRATOR: The semi-submerged vessel is a permanent hazard to passing ships. NICK: The wreck is monitored by CCTV constantly, to avoid the risk of somebody coming out and colliding with it.

NARRATOR: What kind of ship is this? Why is it here? And why is it so dangerous? Diving is difficult, visibility appalling, but, using 3D scan data we can reveal explosive secrets hidden under water. The metal hull of an enormous, 14,000 ton cargo ship emerges. The SS Richard Montgomery. Unseen for 75 years. From a time when London is in the front line of a global war. In 1940, Nazi Germany has taken over much of Europe. Next, Hitler's air force, the Luftwaffe, targets Britain.

ERIC: What the Germans were trying to do was starve Britain out, because Britain depended on overseas supplies. So, therefore, if you could destroy the docks and if you could stop shipping coming up and down the Thames, then you would really affect the British economy and hopefully coerce Britain into a political settlement with Hitler. NARRATOR: The Thames becomes a battlefield. Cargo ships entering the estuary must run the risk of Nazi fire. The details from the drained wreck suggest that the Richard Montgomery is not a victim of an enemy attack.

She's lying in two pieces, with a clean break. The damage is not typical of World War II bombs, torpedoes or sea mines. The drained wreck site reveals a clue. She's sitting astride a large sandbank. To an expert, the Montgomery's design is familiar, it's called a Liberty Ship. And Dr. Nick Bradbeer believes this could shed light on why it sank.

Liberty ships are American made. An emergency response to the large number of merchant ships being sunk by the enemy. US shipyards produce over 2700 Liberty ships during World War II. The most ever made to a single design. The quickest build takes just four and a half days from start to finish. Liberty ships help break Hitler's stranglehold of Europe. ERIC: They were vital components of the Allied Merchant Fleet that effectively provided the foundations of victory.

NARRATOR: But building quick and cheap leads to problems. NICK: Liberty ships have a couple of well-known design flaws, they were made of a grade of steel which became quite brittle in low temperatures. NARRATOR: The ships are not riveted but welded together, which makes them weaker. NICK: Some of the ships simply broke in half at sea. NARRATOR: Delving into historical records, Nick pieces together the Montgomery's last voyage. August 1944, the ship leaves Hog Island, Philadelphia. After crossing the Atlantic it joins a convoy in the Thames Estuary destined for France.

While moored up, strong tidal currents cause her to drag her anchor. NICK: She ran aground over the rafter on a sandbar, and that probably didn't damage her very badly. But, that stuck her in place. NARRATOR: As the tide goes out the 7000 tons of cargo in the ship's hold is no longer supported by water. NICK: She started to bend and bend, and then eventually bent beyond her ability to withstand. NARRATOR: Under high stress, the deck plates fracture.

As time passes, the fracture grows. Until the ship rips apart. Just one question remains, what is it about this wreck that makes it so dangerous? The answer lies in her deadly cargo. NARRATOR: The wreck of the Montgomery endangers shipping and lives. The drained vessel explains why. Some of her cargo can be glimpsed through cracks in the hull.

Bombs. Further research uncovers the full inventory of explosives. Almost 300 2,000 pounders, over ten times as many 1,000 pounders and 2,500 cluster bombs. In total, 1400 tons of explosives lying at the bottom of the Thames. ERIC: Given the combination of the amount of explosives still on the ship and the location of the ship I would say she is probably the most dangerous ship in British waters. NARRATOR: To make matters worse. the wreck lies just 1.5 miles from the town of Sheerness. And four miles from a huge natural gas terminal.

COLIN: It's been suggested it could be the biggest non-nuclear explosion in peace time. People have actually left the island in fear that something was going to happen. NARRATOR: It wouldn't be the first time a Liberty ship explodes. In 1944, US war operations continued to expand, Liberty ships, many packed with ammunition, set off around the world. Near San Francisco, the SS EA Bryan and the SS Quinault Victory are being loaded with ammunition when they both explode.

320 die. And in the Philippines the Liberty ship SS John Burke is hit by a kamikaze aircraft, causing the explosives on board to detonate. 68 are killed. So, could the Montgomery also blow? More clues lie in the drained wreck. Close examination reveals a disintegrating deck house.

And a collapsing deck plate. Failing parts of the ship could eventually hit or dislodge the bombs. Whether it's enough to cause them to detonate, and what the impact of what such an explosion would be, is impossible to know. CLIVE: Lots of people have looked at this, but nobody can give you a guarantee about anything. NARRATOR: To avoid a disaster, the British Government's policy is to cordon off and monitor the wreck.

NICK: It's a difficult situation to know what to do, the risk always has to be balanced between doing something and that potentially actually making the situation worse, or, doing nothing, and monitoring. CLIVE: Nothing's happened much in the last 70 years, that's a fact, and trying to predict the future is difficult. I think if it's monitored and it's managed sensibly it will be fine. NARRATOR: Bloodshed, piracy, ruthless ambition and war. The story of London has it all. And whatever fate has in store, this city and its adaptable, enterprising people, will be at the heart of a world they helped create.