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00:00I'm astonished given what I know about the fragility of the structure that is still standing.
00:30Collapse might be triggered by a storm or an earthquake.
00:39It's very close.
00:59Engineers calculate that this collapse should have taken place years ago. In fact, why the tower is still standing continues to baffle them.
01:08In 1995, Pisa's famous tower was falling over at the rate of about a millimetre a year. That September, an operation to halt this gradual collapse reached a critical phase.
01:30One of those in charge of the engineering was Giorgio Macchi.
01:39We have always been very nervous when we did any intervention on this tower, because the tower is reacting in a way which is not always the way we expect.
01:58Operations continued round the clock, and throughout the first 36 hours went smoothly.
02:07But the patient remained under close observation.
02:16At 3.30 am on the 6th of September, the tower began to move.
02:26In the next 9 hours, it fell as far as it had fallen in the previous 12 months.
02:35The engineers were woken in their beds.
02:40Panic is not the word to use. Worried, yes. Concerned.
02:44And my concern was to get out here as quickly as possible and help in the decision-taking as to how we were going to stop the work, re-stabilise the tower.
02:59The lurch was halted, and an immediate collapse prevented.
03:02But what became known as Black September taught the engineers how even the best of modern science and technology will struggle to save this medieval enigma.
03:21Towers do collapse.
03:24In 1989, in Pavia, a few hundred miles north of Pisa, a 14th century bell tower collapsed, killing four bystanders.
03:39Pavia's tower wasn't even leaning.
03:47That's why the quest to rescue Pisa's tower was launched.
03:50A committee of brilliant minds was assembled the next year, and saving Pisa became one of the great prizes in civil engineering.
04:09Among those taking on the challenge is John Berland of Imperial College London.
04:14When you come in through the west gate and see this glistening white structure looming over the cathedral,
04:23with its lovely symmetry, it is beautiful.
04:26But it's breathtaking, the fact that it hasn't fallen over, that it's just shimmering on the edge.
04:33Berland, a soil engineer, digs into problems below the ground.
04:38But the committee contains equally determined experts who focus elsewhere, like Giorgio Macchi of Pavia University.
04:51A structural engineer, Macchi investigates weaknesses in the tower's masonry.
05:02I work on a structural problem, so I saw immediately the structural risk.
05:13In my opinion, the tower is in real danger.
05:18In 1989, Pisa's dangerous tower was closed to tourists.
05:26It was announced that this should last just three months.
05:34There was little time for delay, but it was felt that late 20th century engineering should make short work of this medieval relic.
05:41But the committee soon became bogged down in arguments which have continued through many meetings over several years.
05:55Conflicting analyses of the tower's problems became the subjects of furious debates, and these disputes were rarely resolved due to a lack of hard evidence.
06:10The tower turned out to be an engineering puzzle that could not be unraveled in the way the committee members were familiar with.
06:23Meanwhile, the tower continued to lean.
06:26The first to put their case were the structural engineers.
06:33They were concerned by a series of massive flaws in the tower which seemed to break all the rules of engineering.
06:40In spite of our knowledge of structures we have as designers or bridges or other structures, I found here special problems.
06:57The shape of the tower is not the usual shape, and every engineering judgment was wrong in this case.
07:06The tower is a hollow cylinder 12 meters wide.
07:13In most places the walls are almost three meters thick.
07:19But corkscrewing through the walls is a staircase wide enough for two Pizans to climb side by side.
07:26An extravagant design, which means that in some places the walls are under one meter thick.
07:31This would be just adequate if the walls were solid marble.
07:34The marble facing is only 25 centimeters thick.
07:41And behind it there is a conglomerate of stones and lime, which is a very, very low resistance.
07:55The infill of stones and lime is not consistent.
07:58There are several large holes in this conglomerate, created by the medieval builders' wooden scaffold.
08:08The holes are some 40 centimeters high holes, so they reduce the resistance area of the wall in a considerable way.
08:18The marble is more than a facade.
08:23It provides most of the support for the 14,000-ton tower, and bears the stress created by the lean.
08:30That's why many of these bricks are breaking up.
08:35Although some of these cracks are superficial, one may be the start of total collapse.
08:42Giorgio Macchi set out to discover if the tower has a flashpoint.
08:56Researchers created a computer model to detect the tower's excessive structural stress, and then highlighted it in blue.
09:08They discovered marble under immense pressure, right below the lean, on the second story, where a doorway meets the staircase.
09:15This is where the tower would collapse.
09:20By calculation we found that this is the really critical point.
09:26And this is shown by the fact that there were very many substitutions of stones in this area.
09:34You can see here is the original stone.
09:40These are completely substituted stones, here and there, and completely substituted in this area.
09:55Because of the tower's immense importance to Pisa, it has always been well maintained.
10:04For centuries, whenever a marble block has become damaged, a new one has been chiseled out and fitted into the tower.
10:16So far this has prevented collapse, but traditional maintenance can no longer contain the extreme stress on the second story.
10:25When the marble here gives way, the tower won't just crumble.
10:34The tensions accumulated over centuries will be instantaneously unleashed,
10:38and the entire structure will be blown to smithereens.
10:41In 1992, in a desperate attempt to contain these forces,
10:57plastic-coated metal tendons were wrapped tight around the second story.
11:00The cracks were clamped shut, but the lean was still increasing.
11:13The committee always knew that a long-term solution for the tower would require a reduction of the lean.
11:26Perhaps with the structure slightly strengthened by tendons, there would be time to develop a technique to achieve this.
11:32The first phase of the research was to identify the original cause of the lean.
11:41As the patient clung to life in intensive care, the engineers began delving into 800-year-old mysteries.
11:48In medieval times, Italy was tower-mad.
11:56Skylines like this one at San Geminiano, just south of Pisa, were commonplace.
12:05For the princes and merchants, the bigger your tower, the more wealth and power you projected.
12:13Today, Pisa is a quiet university town.
12:19But medieval Pisa was an aggressive trading power, and one of the richest cities in the world.
12:29Piero Pierotti is a historian at Pisa University.
12:33Although not on the committee, he is an authority on the tower's past.
12:37It's said that the most important families in Pisa dined off gold plates, because they'd grown very rich from sea-going trade.
12:48And this wealth must have inspired them to do something outstanding for the city.
12:52In 1064, just inside the north wall of the city, work began on a massive cathedral.
13:08The wedding cake-like tiers of marble columns were an early expression of the architectural style that would later embellish the tower.
13:17Inside were more colonnades.
13:27Horizontal layers of black and white marble drew worshippers towards the artistic climax, the apse, with its mosaic of Christ in majesty.
13:38The Pisans planned to give their new cathedral the most extravagant bell tower the world had ever seen.
13:50But this was civic hubris and reached beyond good building practice.
13:54While all the other monuments of the piazza have been signed by their architects, the architect of the tower is unknown.
14:05It's a mystery. Nobody put their name on the tower.
14:09The masons must have realized that the plan for the tower was over-ambitious.
14:15The medieval Pisans were experienced tower builders.
14:20Their suspicions about the cathedral bell tower suggest it was doomed from the start,
14:29and is probably only hanging on thanks to some ancient technique that the masons kept secret.
14:41Architectural historian Jane Morley is not on the committee,
14:45and so is free to voice fears they must keep to themselves.
14:48I don't think anyone, short of God, will understand what it took to build this tower,
14:56and why it's doing what it's doing now.
14:59The people that built this were not scientists or engineers.
15:04They probably had very little formal education. They were builders.
15:07And they had a lot of knowledge.
15:09Knowledge that isn't quantified or codified.
15:13It's what you learn by doing. It's what you learn by being a builder.
15:16With neither plans nor blueprints for the tower,
15:20the past must be deduced from the marble masonry itself.
15:24Carlo Vigiani is an engineer and committee member.
15:27Each stone layer is precise within less than a millimetre.
15:37And this is the reason why we can get so many information by just by measuring these stones.
15:44You can see that in most of these stones there is no mortar at all at the contact between these two stones.
15:51It depends on the high quality of workmanship.
15:54From out of the marble emerges the tortured history of the origins of the lean.
16:03Constructing the tower was a phenomenal achievement, which will enthuse the engineers, even though it will at first bewilder them.
16:10Work began in 1172, and after about six years the masons had reached the fourth level, but then they stopped.
16:26The tower was abandoned for almost a century. This was probably due to political and economic strife.
16:41But perhaps the delay was a brilliant building strategy.
16:48If they'd built the tower in one go, it literally would have fallen over as this one is.
16:54You can just see it settling down.
16:56It's just collapsed.
16:59And that's what would have happened if they'd built it all in one shot.
17:02So what they actually did was, they built the tower up to a little above the third storey, and then they stopped.
17:11And the weight of that tower in that state squeezed the underlying ground.
17:16And over the years the ground became stronger.
17:19So when they came back a hundred years later, it could take the full weight of the tower.
17:25When construction did resume, the masons must have noticed a slight lean to the north.
17:30So as they built upwards, they straightened the tower.
17:36What they did is to have slightly higher stones on the side where the tower was leading.
17:45But as it was straightened, the tower lurched in the opposite direction, south.
17:54And when the masons reached the seventh storey, work stopped again.
17:58Over the next 90 years, the southward lean grew to one and a half degrees, a severe inclination that did not deter the masons from adding a bell chamber.
18:12When they started again to construct the bell tower, they had to make a substantial correction.
18:23And they did it by changing the number of steps according to the direction.
18:27In this side, we are on the north side, we have only four steps.
18:33We will see that on the opposite side, we have six steps.
18:38Now we are on the south side, where the steps are six, just to correct for the inclination.
18:45I feel this tower personally as a challenge.
18:52I cannot conceive the man constructing it knowing that it was previously leaning and going on and finishing it.
19:02Vigiani may be impressed, but thanks to the delays and corrections over generations of masons, the tower doesn't just lean, it's actually shaped like a question mark.
19:13You had different people working on it at different times, with different states of knowledge about what structures like this can do, what they can't do, what happens to them over time.
19:23And you've got different sections of the tower that are different geometries.
19:27So, to write it any degree, you may not get the predicted structural action that you would want.
19:32By the early 90s, years of scientific research had produced a painful conclusion.
19:42The more the leaning tower is studied, the more questions it poses.
19:48But inspired by the example of the medieval masons, the engineers would not give up.
19:54And what's more, they were on the brink of some startling discoveries.
20:02The leaning tower of Pisa is the most intensely scrutinized building in the world.
20:20A surveyor takes readings twice a day.
20:32A circular sensor, which can register the vibration from a single footstep, runs around the inner walls.
20:43Brackets gauge shifts in each of the tower's 25 largest cracks.
20:49Three plumb lines hang from the top level.
20:55Taut cross wires measure deformations in the walls.
21:02Skeptics claim that all the monitors will do is record the collapse in absurd detail.
21:08But discoveries have been made.
21:15The tower reacts to changes in the elements.
21:22Every day, the entire building sways in a minute circle less than 0.2 of a millimetre across.
21:28This infrared camera shows why.
21:35The lens is sensitive to heat, which is displayed as white.
21:41As the sun heats the south side more than the north, the marble here expands, creating an imbalance and motivating the lean.
21:49At night, it will cool down and shrink back.
21:56Larger movements are recorded during rainstorms.
21:58We get these extraordinarily heavy storms in Pisa, and the water table rises very quickly indeed.
22:09And it rises on one side more than on the other.
22:14And it lifts that side, it happens to be the north side.
22:17It lifts the north side a bit so the tower goes to the south when the water table comes up.
22:22Carlo Vigiani has studied the tower for 35 years and is unperturbed by this idiosyncratic behaviour.
22:35Probably in this moment, the tower feels very sad and increases easily.
22:42But when the sun will come back, I say she, probably, and I say it, will come back again.
22:53Sensitivity to the elements suggests the tower was founded in very fluid soil.
22:57Between Pisa and the nearby coast is an alluvial marsh.
23:10The engineers suspect this is what the ground around the tower looked like before construction began.
23:15On the marsh's exposed shoreline, John Berland investigated what effect this soil would have upon the tower.
23:34Well, about 10,000 years ago, the location of the tower was actually a river estuary.
23:40And the tide would come in and out, and the floods would come down each year.
23:46And they'd deposit sand and silt.
23:50Well, the soil beneath the tower was actually very much like this beach.
23:56It's soft. You sink into it.
24:00And that's what they actually built the tower on.
24:02And the reason why it's leaning is because the soil on the south side is just a little bit more compressible than on the north side.
24:19In Bergamo, in the far north of Italy, a team of scientists performs an ingenious experiment
24:24in which they attempt to reconstruct Pisa's geological history.
24:39An aluminium model of the tower, less than a metre high, is placed upright on sand which has been carefully arranged to mimic the silt below Pisa's tower.
24:49Sandy silt and metal tower are then lowered into a centrifuge, which will create immense pressures to simulate the effect of hundreds of years of gravity.
25:07Sandy silt and metal tower are then lowered into a seizing of gravity.
25:20Centuries are compressed into weeks.
25:25As the mercury is suppressed into the silt.
25:30The strength of the earth is враг.
25:33As the model is taken out of the centrifuge, it leans just like the real thing.
25:46When disassembled, the experiment reveals how the tower sank lopsidedly through soil
25:51as soft and inconsistent as a beach.
25:57Such investigations have revealed why the lean began.
26:00The hope is that this research will help in developing a technique to reverse the lean
26:05and so save the tower.
26:16The tower has always been cared for by a board of works called the Opera, whose presidents
26:21represent an unbroken line of craftsmen right back to the 11th century.
26:35In the Opera archives are thousands of schemes for the leaning tower, sent in from all over
26:41the world.
26:44Some were devised by qualified engineers, others by schoolchildren.
26:53Other schemes involve propping.
26:55But a huge prop would be unacceptable in the historic Italian piazza and would probably
27:01destroy the tower anyway.
27:02A lot of people say, why can't we just prop it or why can't we just push it back?
27:08And this experiment shows why that's about the most dangerous thing you could do, in fact.
27:13The masonry is represented by this acrylic cylinder.
27:17And this weight here applies weight to the top of the tower.
27:22We'll increase the inclination of the tower and prop it or push it and you can see what
27:29happens.
27:30It just literally collapses.
27:34By the early 90s, the committee still hadn't agreed a plan for the permanent reversal of
27:39the lean.
27:40So they decided to compromise, to be less ambitious.
27:49We felt that the tower was very close to falling over and we needed to do something urgently
27:54to temporarily stabilise it.
27:58The engineers looked through previous studies of the tower.
28:02The first precise measurements were made in 1817 by two British architects, Edward Creasy
28:08and George Taylor.
28:10The lean was just over five degrees, but this was a static observation.
28:17Regular surveys have been made since 1911.
28:20And from study of this data, a breakthrough was achieved.
28:24The tower has stopped settling into the silt.
28:31The ground has hardened and the tower is no longer sinking.
28:35It's tilting over, capsizing.
28:41And as soon as we discovered that, we thought, ah, if this side is coming up, then it's rather
28:50like sitting on a sailing boat.
28:52If you can just lean out, you can pull it back a little bit.
28:58Maybe it would be safe to put temporarily some load here to reduce the tendency for the tower
29:05to fall over.
29:13In July 1993, the contractor started piling 600 tons of lead ingots on the rising north side.
29:24The danger was that the ground might give way again and the tower start to sink, then crash.
29:32We did this very gradually over a four or five month period, putting the lead weight on, leaving
29:38it for a day, making measurements, putting another one on and so on.
29:45As an emergency stabilisation, the lead ingots worked.
29:48For the first time in 800 years, the lean was under control.
29:53But by then, the beautiful tower had become an eyesore.
29:58Berlin had an alternative solution which he believed would provide long-term security for
30:03the tower.
30:05This model demonstrates the soil extraction technique.
30:12We drill in under the tower with a specially designed drill which causes no disturbance to
30:18the ground.
30:19And when it's at the location we want it, we can then gently pull the drill out.
30:24So if we look at this, the soil will then close in the cavity and we'll see the tower rotating
30:31back towards the north side as we under-excavate.
30:37A 10% reduction in inclination will reduce the stresses by 10% in the masonry and that's
30:46a very reasonable amount.
30:52In Pisa, a concrete test tower has been constructed.
30:56It's taller and heavier on the south side and so applies the same force on the ground as
31:01the real leaning tower.
31:03Here, a full-scale experiment is underway.
31:07And we were extracting soil over a length of this sort and you can see here how the ground
31:14has subsided and that brought the whole trial footing northwards by about half a degree.
31:23But members of the committee had their doubts.
31:27Such intervention has been tested on a specimen and this works very well.
31:34But to extend this intervention under the tower in this special situation which has been formed
31:42within 700 years, there is still a residual risk and the committee is thinking about that.
31:59At tense committee meetings, Carlo Vigiani was a lonely apostle for soil extraction.
32:05If we go back by half a degree, then even if the worst happens, which is that the tower
32:14starts to move again as soon as we leave it, we'll have more than 300 years ahead of us.
32:19I'm a bit puzzled by what Carlo is saying.
32:26What do you mean go back 300 years?
32:30With so much at stake, it was hard to reach an agreement, especially with so many experts.
32:44What is very peculiar of this committee is that it is a multidisciplinary committee.
32:51There are people from this side of history of art, of restoration and engineers, geotechnical
32:58engineers, structural engineers.
33:01And it is not easy to work together for such differently minded people.
33:06The people who are not technical have to be convinced that what we want to do is appropriate
33:20for the tower and safe.
33:22So it's incumbent upon the engineers to explain to them in simple terms what it is they are
33:29wanting to do and why it will be effective.
33:39But by the mid-90s, the committee was no longer attracted to soil extraction.
33:45Instead, they were about to opt for an alternative solution, which was to bring the tower closer
33:55to collapse than it has ever been.
33:58There have been 16 committees to save the leaning tower of Pisa.
34:16And there have been many previous interventions.
34:19All have failed.
34:24The most disastrous and instructive meddling was the digging of a trench around the base.
34:31This is called the Catino.
34:33It's a walkway.
34:35And it was excavated by an architect called Gerardesca in 1838.
34:41Now, it's important to remember that the tower has settled about three metres since it was built.
34:49As a result of the settlement, the base of the columns on the ground floor had become buried beneath the ground.
35:00And Gerardesca argued that it would be lovely to reveal them so that people walking around the piazza
35:07could view the base of the columns as the original architect had intended them to be.
35:13So he just came in and dug this out.
35:16And he dug down about one and a half, two metres down.
35:21And this is the wall of the Catino.
35:23What he didn't realise was that the water table is about here.
35:28So there's a lot of water behind this wall and under the foundations.
35:34And as he dug this Catino out, the water came spouting out of the ground.
35:40And the tower moved.
35:43The top of the tower moved about half a metre.
35:45It lurched, literally, this way.
35:48It's amazing that it didn't fall over.
35:51At least this dreadful history tells the present committee what not to do.
35:56When anybody has tried to do anything on the south side, the tower has always said,
36:02don't touch me.
36:03I'm very, very delicate.
36:05And it's moved.
36:07So the tower has actually spoken to us through the way that it's moved.
36:12So caution is wise.
36:14But visitors to the tower have been growing impatient.
36:17By the mid-90s, Pisa's vital tourist industry appeared to be struggling.
36:29Through this elegant window, the committee had a clear view of what they had achieved after five years of debate.
36:36The hideous lead ingots.
36:38In desperation, they turned to Maki and the structural engineers who proposed a high-risk subsoil intervention.
36:47The committee would like first to remove the lead waste and to substitute them with invisible cables in the soil, giving the same effect.
37:02In this plan, anchors would be attached to a concrete ring wrapped around the base of the tower.
37:09These would then be drilled through the soft soil and secured in the solid bedrock 40 metres down.
37:15The pull from the anchors would replace the push of the unattractive lead weights.
37:28In 1995, contractors attempted to install the ring through which the anchors would be connected to the tower.
37:35The reinforced concrete ring was constructed under the catino, beneath the water table.
37:54So as the contractors burrowed down, liquid nitrogen, which has a temperature of almost 200 degrees below zero, was injected into the soil.
38:03Any ground water should be frozen solid and so could not flow into the diggings.
38:09This precaution triggered the events locals came to know as Black September.
38:14It was in September.
38:25Throughout this difficult period, safeguarding the Piazza dei Miracoli was the responsibility of the opera president, Ranieri Favilli.
38:33There was a time in which, to tell the truth, I began to imagine I was hearing strange noises during the night.
38:46I can't say I didn't worry about this.
38:48Unfortunately, it's inevitable because, first of all, I'm a Pisan.
38:52And secondly, I would frankly be very unhappy to go down in history as the opera president under whom the tower fell.
39:04It was shortly after the freezing process moved to the sensitive south side that, on the 6th of September, the top of the tower lurched one and a half millimeters south.
39:27In one night it moved what it normally moved in a year.
39:35And that worried us because if that had continued, that would have been very large and the tower's stability may have been in jeopardy.
39:43Berlin flew out to Pisa where he was joined by Giorgio Macchi, one of the scheme's main advocates.
39:57Perhaps because there was no fractious committee to dispute it, a re-stabilization plan began almost immediately.
40:04The lurch was halted by piling on 300 tons more lead.
40:15The attempt to remove this eyesore only made it worse.
40:19But later Macchi makes light of Black September.
40:23There was a so small, so small inclination southward that it would be nearly impossible to measure with the old means.
40:34But we knew that the tower was moving, was responding in a special way, and we decided to stop the tower.
40:46This committee, what has it done?
40:52It's intervened basically in that same highly delicate zone where Gerardeska had intervened.
40:57And all they did is bring the tower closer to collapse.
41:01One would believe if one were of a late 20th century technocratic mentality, or just simply have a faith in science.
41:13Well, we know so much, why can't we come up with a solution to the problem?
41:17But there may be in fact no solution.
41:23For the next year, the building site around the tower remained quiet.
41:30Then, in late 1996, the committee was disbanded.
41:35Their extensive research may have been a complete waste of time and effort.
41:43It's been very frustrating.
41:45A lot of my friends say to me, how can you possibly stand the way this has gone on and on and on and on?
41:53Why don't you just resign? It would be so much easier.
41:56But it's so important to the life of the tower that we do something soon.
42:01The committee remained out of action until, in autumn 1997, north of Pisa, near Assisi, birthplace of St. Francis, an earthquake hit measuring almost six on the Richter scale.
42:16Thousands were left homeless.
42:23Unique historic buildings were damaged beyond repair.
42:28Irreplaceable Renaissance treasures were lost forever.
42:34It soon emerged that although this earthquake was no surprise, little had been done to prepare for it.
42:46The resulting scandal inspired a new dynamic attitude in Italian restoration and conservation.
42:52In Pisa, the committee was reconvened, had a change of heart and, in late 1998, finally approved soil extraction.
43:07Now we're faced with the reality of doing something on the tower for the first time.
43:13Something very delicate and something that we hope will provide the final solution.
43:19There is no margin for error left now.
43:24So before the final solution begins, the engineers will weave a network of steel cables into a harness for the tower.
43:32The harness is a temporary safeguard structure.
43:38It's there to make quite certain that if something goes wrong, we can control it.
43:45It's only temporary, it'll only be there when we're operating on the tower.
43:52During an unsettling deluge, the first cable of the harness is craned into position.
44:03Although only temporary, this is a huge project.
44:07Just ten yards of this cable weighs half a tonne.
44:15If it lashes out from the crane, it could kill the workmen and damage the fragile tower.
44:27The cable slips and jams into a marble arch.
44:37Hours later, the struggle to free the cable is successful.
44:50That night, the first component of the harness is secured.
44:54The completed harness appears to be an attempt to prop the tower.
45:15But propping had previously been dismissed.
45:18In fact, these hefty cables anchored to massive tripods are finely balanced and apply very little force to the fragile masonry.
45:31The harness is not intended to stop a catastrophic failure.
45:37It's not for that at all.
45:38It's simply to hold the tower gently if the movements of the tower are unexpected.
45:44By February 1999, after nearly a decade of waiting, the scene is set for the final act.
46:09We have just started soil extraction.
46:12The drill is about five metres below ground level.
46:19And then the soil extraction takes place beneath the floor of the Catino.
46:25And the effect extends out.
46:29As we take the soil out, the effect of it extends under the tower.
46:33The success of soil extraction hinges on the assumption that the ground below the tower is almost pure silt.
46:46On day one, 27 litres of soil spew out of the extractor casing.
46:50But it looks like clay, not silt.
46:52Not silt.
46:55Berlin is quick to make an on-the-spot analysis.
46:58An experienced soils engineer can tell exactly what the soil material is.
47:03If you just put a grain or two against your teeth, you can tell straight away that this is actually a sandy silt.
47:15It feels like clay, but it's actually sandy silt.
47:17So it's total confirmation of what we were expecting.
47:23The tower has been creeping south for centuries, and so the lean will not be reversed in a few hours.
47:33Right now, the main fear is that the drilling will trigger a catastrophic movement further south.
47:52But the monitors reveal there is no negative response from the tower.
47:56We have started what could well turn out to be the final stabilisation measures.
48:05The result will be that the tower will be leaning at 10% less than it is now,
48:12and we will have added 300 years to its life at least, and we will have reduced the stresses in the masonry.
48:20And these have been our prime objectives right from the start of the whole project.
48:24After two months of soil extraction, the top of the tower has moved back six millimeters.
48:48Finally, the medieval enigma appears to be coming under the control of the engineers.
48:54But the stable position of 300 years ago lies a further half-meter north.
49:00Even if the operation continues to go well, it will take two years to move the tower this far.
49:07Until then, the leaning tower of Pisa will remain wired in and strapped up,
49:13like a hospital patient on an operating table, hardly out of intensive care.
49:17For an online chat with the director of tonight's programme and more information about the leaning tower of Pisa, visit the Channel 4 website.
49:35Next week, an investigation into one of the most decent countries on Earth,
49:40which sterilised thousands of its citizens up until 1975.
49:44Equinox at nine.
49:46Equinox at nine.
49:47Equinox at nine.
49:48Equinox at nine.
49:53Equinox at nine.
49:56Equinox at nine.
49:59Equinox at nine.
50:00Equinox at nine.
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