0:00:17 > 0:00:22These are the rolling fields of Picardy in northern France.
0:00:22 > 0:00:24It looks beautiful this evening,
0:00:24 > 0:00:28but it was once the scene of some of the most appalling carnage
0:00:28 > 0:00:30in military history.
0:00:30 > 0:00:33This is the epicentre of the Somme battlefield.
0:00:33 > 0:00:37EXPLOSIONS
0:00:37 > 0:00:39The first day of the Battle of the Somme
0:00:39 > 0:00:43was the greatest British military disaster of the First World War.
0:00:46 > 0:00:50The village below us is La Boisselle,
0:00:50 > 0:00:55and on 1st July 1916 in the valleys to either side of it
0:00:55 > 0:00:5911,500 men became casualties - the highest concentration
0:00:59 > 0:01:02on the entire battlefield that dreadful day.
0:01:05 > 0:01:09We know a great deal about the killing fields of the Somme,
0:01:09 > 0:01:11but in fact there was another battlefield here,
0:01:11 > 0:01:15a private battlefield and it lies beneath my feet.
0:01:20 > 0:01:23This is one the great mysteries of the Somme -
0:01:23 > 0:01:27the hidden networks of tunnels that sleep beneath its villages and fields.
0:01:31 > 0:01:34Here, British tunnellers fought a brutal underground war,
0:01:34 > 0:01:37planting huge mines to destroy beneath the German front line.
0:01:44 > 0:01:47Mines were the original weapons of shock and awe.
0:01:49 > 0:01:52Their detonation at Le Boisselle on 1st July 1916
0:01:52 > 0:01:56should have signalled the beginning of the end of the war.
0:01:59 > 0:02:01To get under the German lines,
0:02:01 > 0:02:05tunnellers had to play a terrifying game of blindfold cat and mouse.
0:02:06 > 0:02:08To lose probably meant death.
0:02:09 > 0:02:11You never knew where the enemy was.
0:02:11 > 0:02:15He could be 40 metres away, he could be 40 centimetres away,
0:02:15 > 0:02:19but the more noise you made, the less likely you were to survive.
0:02:22 > 0:02:26But who were the men who fought in this subterranean battlefield?
0:02:26 > 0:02:29And why, in the end, did British High Command fail to press home
0:02:29 > 0:02:33the tactical advantage the tunnellers had given them?
0:02:35 > 0:02:39Now we've been given the opportunity to explore these tunnels,
0:02:39 > 0:02:41to find out what those men did.
0:02:42 > 0:02:45Their story is the last great secret of the Battle of the Somme.
0:03:07 > 0:03:10Whilst La Boisselle has now been rebuilt and the land returned
0:03:10 > 0:03:15to agriculture, this crater field - the physical legacy of war -
0:03:15 > 0:03:19is one of only a handful of untouched sites on the Somme today.
0:03:21 > 0:03:26An invitation from the family that owns the land provided us with a unique opportunity
0:03:26 > 0:03:31to investigate what happened to those who fought here, especially the tunnellers.
0:03:33 > 0:03:36It all started with a hole in the ground.
0:03:38 > 0:03:42It's quite tight here, but it's OK.
0:03:43 > 0:03:46I can see a long way down it. It is clear.
0:03:47 > 0:03:51'This is the strange world on which the novel Birdsong was based.
0:03:51 > 0:03:54'Until now, it could only be imagined.'
0:03:54 > 0:03:57- I'll just go a wee bit further.- OK.
0:03:57 > 0:04:00'We know 1,000 men once worked here.'
0:04:05 > 0:04:10Keep your belly flat to the ground, it opens out pretty quickly.
0:04:14 > 0:04:16'Our first venture underground proved remarkable.'
0:04:16 > 0:04:19You can see to the end of the gallery.
0:04:19 > 0:04:23'Above us, the evidence of the struggle has faded beneath the plough.'
0:04:23 > 0:04:28There's candle burns here and there, but some of the wall has peeled off.
0:04:31 > 0:04:36'Down here in the shadows we find a labyrinth, clearly intact -
0:04:36 > 0:04:38'long hidden, still dangerous.'
0:04:41 > 0:04:46Let's have a look. See if I can get down here.
0:04:46 > 0:04:47A little bit tight, just here.
0:04:49 > 0:04:51There's air pipe here.
0:04:51 > 0:04:53Is the air pipe connected up?
0:04:53 > 0:04:55No, it's just loose pieces.
0:05:02 > 0:05:06'For the most part, history has overlooked the tunnellers' role
0:05:06 > 0:05:09'and their primitive war has remained mysterious.'
0:05:09 > 0:05:13Plenty of timber. 'But we soon found evidence of their character.'
0:05:13 > 0:05:17Oh! There's writing here.
0:05:17 > 0:05:20- Graffiti?- Writing, yeah.
0:05:22 > 0:05:26Look, you can see the pick mark here, of the man who's cut that out.
0:05:26 > 0:05:30And on this face, which has been cleft, is this extraordinary poem.
0:05:30 > 0:05:34I wish we could read the name of the author.
0:05:34 > 0:05:38"If in this place you are detained, don't look around you all in vain,
0:05:38 > 0:05:42"but cast your net and you will find that every cloud is silver lined.
0:05:42 > 0:05:45"Still." Look at that, "still."
0:05:45 > 0:05:49Those last five letters are really remarkable.
0:05:49 > 0:05:51"Still", the word "still".
0:05:51 > 0:05:56That speaks volumes because the man who wrote this,
0:05:56 > 0:05:59he's right in the jaws of death.
0:05:59 > 0:06:01"That every cloud is silver lined, still."
0:06:01 > 0:06:04MUSIC: "Good-bye-ee" By RP Weston and Bert Lee
0:06:04 > 0:06:06# I'll be tickled to death to go
0:06:06 > 0:06:07# Don't cry-ee
0:06:07 > 0:06:09# Don't sigh-ee
0:06:09 > 0:06:12# There's a silver lining in the sky-ee
0:06:12 > 0:06:15# Bonsoir, old thing, Cheerio, chin, chin
0:06:15 > 0:06:17# Nah-poo, toodle-oo, goodbye-ee! #
0:06:23 > 0:06:26The village of La Boisselle lies on the Roman road from Bapaume
0:06:26 > 0:06:30to Albert, with the cities of western France beyond -
0:06:30 > 0:06:32an ancient axis of invasion.
0:06:35 > 0:06:40In the autumn of 1914, for the second time in 50 years,
0:06:40 > 0:06:43an invading German army marched down this hill,
0:06:43 > 0:06:47and it was here at La Boisselle that their progress was finally halted.
0:06:53 > 0:06:58This is one of the earliest maps produced of La Boisselle.
0:06:58 > 0:07:02It's a French one and it shows us exactly what the village was like
0:07:02 > 0:07:07at the onset of positional warfare, at the onset of trench warfare.
0:07:07 > 0:07:10The Germans were driving through on this axis,
0:07:10 > 0:07:11pushing through the village,
0:07:11 > 0:07:14trying to take Albert and Amiens and then curve around to Paris.
0:07:14 > 0:07:17The French were coming in this direction,
0:07:17 > 0:07:22pushing up the same axis and everything came to a stop
0:07:22 > 0:07:23just here.
0:07:27 > 0:07:30A contemporary German postcard depicts the fight for the village
0:07:30 > 0:07:35as a glorious triumph, but one eyewitness described it as,
0:07:35 > 0:07:39"Hell on Earth, which no living thing could survive",
0:07:39 > 0:07:42such was the intensity of the fighting.
0:07:43 > 0:07:46Another recorded that, "No sign of life appeared
0:07:46 > 0:07:50"over the surface of the ground. Even the grass was withered
0:07:50 > 0:07:54"by the fumes of high explosive - death, indeed, was emperor here."
0:07:57 > 0:07:59La Boisselle was a cauldron.
0:08:07 > 0:08:10The bitterest fighting was over the civilian cemetery.
0:08:10 > 0:08:14And for a farm on the western edge of the village - it stood here -
0:08:14 > 0:08:16this is all that's left of the courtyard.
0:08:17 > 0:08:21The remains of the farm is where the story of tunnelling
0:08:21 > 0:08:22at La Boisselle begins.
0:08:24 > 0:08:27This is all that remains of that farm. This is the Granathof -
0:08:27 > 0:08:30literally "exploded farm" - the name given to it by the Germans.
0:08:30 > 0:08:33The French called it the Ilot.
0:08:33 > 0:08:36And the fighting over this farm was so bitter,
0:08:36 > 0:08:38between the French Breton troops and the Germans,
0:08:38 > 0:08:43hundreds of people lost their lives fighting over a farmyard.
0:08:46 > 0:08:47Which way is he lying?
0:08:52 > 0:08:58There was a chest here, and probably one arm here.
0:08:58 > 0:09:02- So his head is over here? - Probably somewhere here.
0:09:02 > 0:09:04So he's lying in this direction?
0:09:04 > 0:09:07Yeah. In fact he's just like that, with the hands...
0:09:09 > 0:09:13And probably there was the rifle here.
0:09:13 > 0:09:15- This is his rifle?- Yeah.
0:09:15 > 0:09:19'Breton troops fought against heavy odds to hold back the enemy here.
0:09:21 > 0:09:25'Their homeland and their pride was at stake.'
0:09:25 > 0:09:29The French were not to withdraw behind the existing front line,
0:09:29 > 0:09:33because they have bought that front line with
0:09:33 > 0:09:35the lives of hundreds of their men.
0:09:36 > 0:09:40And if that line was to be lost, if that line was to be given up,
0:09:40 > 0:09:42it would be a betrayal of that sacrifice.
0:10:02 > 0:10:05After only four and a half months of fighting,
0:10:05 > 0:10:09by Christmas/New Year 1915, the war had descended into stalemate.
0:10:09 > 0:10:14These flags here, the yellow flags, they represent the French front line
0:10:14 > 0:10:16and the red ones, the German front line.
0:10:16 > 0:10:19You can see how close together they are.
0:10:19 > 0:10:23And what was about to take place was almost medieval -
0:10:23 > 0:10:28trench against trench, static warfare, siege warfare.
0:10:28 > 0:10:30The trenches were fortifications on both sides.
0:10:30 > 0:10:33In between you had no-man's-land.
0:10:33 > 0:10:36And that was the perfect environment for military mining.
0:10:38 > 0:10:43It was on Christmas Day 1914 that French engineers
0:10:43 > 0:10:46sank their first shaft at this very point.
0:10:46 > 0:10:50And that was the beginning of a colossal struggle.
0:10:52 > 0:10:56The huge crater made by the German mine that obliterated the Granathof
0:10:56 > 0:11:00reveals the devastating nature of tunnel warfare - whether they
0:11:00 > 0:11:05liked it or not, both sides were now locked in to subterranean conflict.
0:11:06 > 0:11:08There was nowhere to hide from a mine -
0:11:08 > 0:11:13it could destroy a trench and its occupants in an instant.
0:11:13 > 0:11:17For the infantry, even the suspicion that they were
0:11:17 > 0:11:20being undermined created a paranoia that quickly eroded morale.
0:11:22 > 0:11:28Within 12 months, no-man's-land was a chain of craters and in fact
0:11:28 > 0:11:34what happened was, as the explosive charges grew and grew in scale,
0:11:34 > 0:11:38the two opposing sides blew each other further apart.
0:11:46 > 0:11:50Tunnelling had long been a valuable tactic when enemy positions
0:11:50 > 0:11:55proved impregnable, or in the case of a castle or fortress, immovable.
0:11:55 > 0:11:58Military mining is as old as siege warfare itself.
0:12:03 > 0:12:06It would be a mistake to think that military mining
0:12:06 > 0:12:09and tunnelling was born in the First World War.
0:12:09 > 0:12:12In fact, it has a 4,000-year history.
0:12:12 > 0:12:16But there's only a handful of places on Earth where you can visit
0:12:16 > 0:12:18an early mine, and this is one of them.
0:12:18 > 0:12:22I'm on the east coast of Scotland at St Andrews Castle,
0:12:22 > 0:12:28and beneath us here is not only an offensive mine but a counter mine -
0:12:28 > 0:12:32the defence, coming down to meet the offence, and that is what
0:12:32 > 0:12:36mining and tunnelling in the First World War was all about.
0:12:40 > 0:12:44In 1546, a band of Protestant reformers and rebels
0:12:44 > 0:12:45were besieged here.
0:12:48 > 0:12:52When they detected noises suggesting the fort tower was being undermined,
0:12:52 > 0:12:57they themselves started digging to intercept the incoming offensive tunnel.
0:13:03 > 0:13:06You can see how the offensive tunnel just here
0:13:06 > 0:13:10is dipping very steeply down - that's to get underneath the ditch.
0:13:10 > 0:13:14The next target is that fort tower, and there
0:13:14 > 0:13:17they would have dug a chamber out and packed it with gunpowder.
0:13:18 > 0:13:21The reason why this place is so big is
0:13:21 > 0:13:24because they were using pack animals to remove the spoil,
0:13:24 > 0:13:27so donkeys or mules to carry it out up the steps.
0:13:27 > 0:13:31The steps are original, but of course at La Boisselle,
0:13:31 > 0:13:34those pack animals were the poor bloody infantry.
0:13:34 > 0:13:38The key part of this system is just up ahead here.
0:13:44 > 0:13:47This is the essence of military mining,
0:13:47 > 0:13:50this is where the two tunnels met. The defence coming down here,
0:13:50 > 0:13:53having heard these guys tunnelling towards them,
0:13:53 > 0:13:55to stop them undermining the fort tower,
0:13:55 > 0:13:59and the offence suddenly finding they are face-to-face with the enemy.
0:14:06 > 0:14:10One of the strange thoughts that occurs to me crawling through this place...
0:14:12 > 0:14:16..is that you could take any one of the tunnellers who worked here -
0:14:16 > 0:14:18offence, defence, doesn't matter -
0:14:18 > 0:14:20transport him 500 years into the future,
0:14:20 > 0:14:23put him in a First World War uniform,
0:14:23 > 0:14:25set him to work at La Boisselle
0:14:25 > 0:14:30and within five minutes, he would know exactly what to do.
0:14:30 > 0:14:33And that's because the methods for military mining
0:14:33 > 0:14:38did not change one jot in 500 years, because they simply didn't have to.
0:14:38 > 0:14:40Quick march!
0:14:49 > 0:14:53Throughout 1915, the French were losing men hand over fist.
0:14:53 > 0:14:56And the British were forced to take over,
0:14:56 > 0:15:01to relieve them of more and more sectors down the Western Front -
0:15:01 > 0:15:04Vimy, Arras and eventually on the Somme.
0:15:04 > 0:15:07And it was at the end of July 1915
0:15:07 > 0:15:09that the Black Watch arrived here, at La Boisselle.
0:15:13 > 0:15:16And, on this plan, we can see
0:15:16 > 0:15:18when the Black Watch arrived,
0:15:18 > 0:15:21these shafts are actually untenable.
0:15:21 > 0:15:25They're not deep enough, they're being blown apart by German mines,
0:15:25 > 0:15:29so they've had to step back to give themselves space
0:15:29 > 0:15:31to get underneath the Germans,
0:15:31 > 0:15:34to undermine the Germans.
0:15:34 > 0:15:37In trench warfare, if you're looking down upon your enemy,
0:15:37 > 0:15:38you have all the advantage.
0:15:38 > 0:15:41In tunnel warfare, you're better off underneath him.
0:15:46 > 0:15:51Scone Street trench, originally dug by the French,
0:15:51 > 0:15:56but they were all renamed by the Scots when they arrived in July 1915.
0:15:56 > 0:15:58And this was a main thoroughfare,
0:15:58 > 0:16:01this is the very first entrance ever dug by those men.
0:16:07 > 0:16:10The tunnels and trenches around Scone Street
0:16:10 > 0:16:11occupied by the Black Watch
0:16:11 > 0:16:14are where we begin our deeper excavation.
0:16:26 > 0:16:27Good morning, all.
0:16:27 > 0:16:29- Good morning.- Good morning!
0:16:29 > 0:16:31Welcome to our new arrivals.
0:16:31 > 0:16:34It's frankly been unbelievable,
0:16:34 > 0:16:36what we've found, what we've learnt.
0:16:36 > 0:16:41Every single minute we've been here has thrown up new information
0:16:41 > 0:16:43which has been very, very surprising.
0:16:50 > 0:16:52We're working on the surface
0:16:52 > 0:16:55and we're working underground at the same time.
0:16:55 > 0:16:58We don't have any objectives cos we don't know what we're going to find,
0:16:58 > 0:17:00so we cannot place any objectives.
0:17:00 > 0:17:01When you believe you know so much,
0:17:01 > 0:17:04you find something, you realise just how little you know.
0:17:04 > 0:17:07Really astonishing, what we're finding.
0:17:10 > 0:17:12It's hard to know what to say, isn't it?
0:17:12 > 0:17:15Imagine how easy it is to miss that.
0:17:17 > 0:17:19By the summer of 1915,
0:17:19 > 0:17:23the scale of operations at La Boisselle had dramatically increased.
0:17:23 > 0:17:28At Scone Street, we uncover a prime ingredient of mine warfare.
0:17:28 > 0:17:30Boxes of guncotton explosive.
0:17:32 > 0:17:34And evidence of other materials
0:17:34 > 0:17:37vital to maintain huge armies on a static battlefield.
0:17:39 > 0:17:41- I think, yeah.- What is that for?
0:17:41 > 0:17:46Petrol tin, probably a petrol tin, used for carrying water.
0:17:46 > 0:17:48When the armies came in here,
0:17:48 > 0:17:52the natural population just shot up from a few thousand
0:17:52 > 0:17:54to hundreds and hundreds of thousands of men.
0:17:54 > 0:17:56There wasn't enough water for these men
0:17:56 > 0:17:58and all the horses and everything.
0:17:58 > 0:18:00So, when the tunnelling started,
0:18:00 > 0:18:04they sank wells down through the water table
0:18:04 > 0:18:07in other to draw water from 110 feet down
0:18:07 > 0:18:08to serve the men in the trenches.
0:18:08 > 0:18:11So the tunnels served three purposes -
0:18:11 > 0:18:13one, to defend your own trenches,
0:18:13 > 0:18:15two, to kill the enemy, three, to supply water.
0:18:15 > 0:18:17Without water, you can't fight a war.
0:18:17 > 0:18:19So no water, no war.
0:18:25 > 0:18:27It didn't take the British long
0:18:27 > 0:18:29to bequeath fresh names at La Boisselle.
0:18:29 > 0:18:33The French "Ilot" was rechristened the Glory Hole,
0:18:33 > 0:18:35a title that came to hold fearsome undertones
0:18:35 > 0:18:37for the soldiers who served there.
0:18:45 > 0:18:48This is what the sector looked like soon after the British arrived.
0:18:52 > 0:18:56The French tunnels they inherited were unconnected,
0:18:56 > 0:18:58low, narrow, airless,
0:18:58 > 0:19:01hazardous and too shallow to be effective.
0:19:08 > 0:19:12Improving the situation required skills that the Army did not have.
0:19:14 > 0:19:17Until the arrival of a new kind of Royal Engineer unit.
0:19:18 > 0:19:21Made up of professional tunnellers and miners,
0:19:21 > 0:19:24specially drafted in for their underground expertise.
0:19:26 > 0:19:31The Tunnelling Companies were the brainchild of one extraordinary man.
0:19:35 > 0:19:37One, two, three.
0:19:39 > 0:19:41This manhole, here in Manchester,
0:19:41 > 0:19:44introduces one of the great characters of the tunnelling story.
0:19:44 > 0:19:49John Norton-Griffiths, he was a millionaire, entrepreneur, engineer
0:19:49 > 0:19:50and it was his men
0:19:50 > 0:19:54who were digging the sewers in 1913 beneath Manchester.
0:19:59 > 0:20:00When war was declared,
0:20:00 > 0:20:03Norton-Griffiths' company was building an extension
0:20:03 > 0:20:05to Manchester's main drainage system.
0:20:07 > 0:20:10He relied on a unique breed of workers
0:20:10 > 0:20:13to dig through the clay geology of the area.
0:20:13 > 0:20:15They were known as clay-kickers.
0:20:15 > 0:20:18Norton-Griffiths called them his "moles".
0:20:20 > 0:20:24It so happened that Lord Kitchener, Secretary of State for War,
0:20:24 > 0:20:26was a family friend.
0:20:27 > 0:20:29Norton-Griffiths wrote to him
0:20:29 > 0:20:33proposing that clay-kickers might be very useful to the Army.
0:20:39 > 0:20:43Norton-Griffiths, of course, wasn't suggesting to Kitchener
0:20:43 > 0:20:46that his moles should be digging huge sewer-like structures,
0:20:46 > 0:20:49as we saw beneath the streets of Manchester.
0:20:49 > 0:20:52No, what he was saying was that his men, his moles,
0:20:52 > 0:20:55could dig small, narrow, constricted tunnels
0:20:55 > 0:20:58which will get underneath the German lines swiftly,
0:20:58 > 0:21:02but, most important of all, silently.
0:21:02 > 0:21:05None of the British military establishment believed
0:21:05 > 0:21:08that the war was going to extend beyond Christmas at that time,
0:21:08 > 0:21:12so the letter was simply filed under "M" for moles.
0:21:16 > 0:21:19In December, the Germans blew the first mines
0:21:19 > 0:21:21beneath British positions.
0:21:21 > 0:21:23More and more followed.
0:21:23 > 0:21:26By mid January, panic rippled through the trenches
0:21:26 > 0:21:28and the War Office.
0:21:28 > 0:21:30Norton-Griffiths is called in by Kitchener
0:21:30 > 0:21:34and he demanded 10,000 clay-kickers.
0:21:34 > 0:21:36There weren't that many in the country,
0:21:36 > 0:21:38but it put Norton-Griffiths in charge.
0:21:41 > 0:21:44There was no time for military niceties.
0:21:44 > 0:21:47On Thursday, 18 February 1915,
0:21:47 > 0:21:51the first party of 20 kickers were told to leave this very sewers.
0:21:51 > 0:21:54Later that same day, they arrived here,
0:21:54 > 0:21:56at John Norton-Griffiths' London offices,
0:21:56 > 0:21:59where they were attested and given a medical.
0:21:59 > 0:22:03The 18 that passed were immediately dispatched to Victoria Station
0:22:03 > 0:22:06for the next leg of their journey to an unknown destination.
0:22:08 > 0:22:10The next stop was here -
0:22:10 > 0:22:12Brompton Barracks, in Chatham, Kent,
0:22:12 > 0:22:13home of the Royal Engineers.
0:22:13 > 0:22:18So our 18 sewer drivers have arrived with no military training whatsoever
0:22:18 > 0:22:21to be inducted into one of the most illustrious corps
0:22:21 > 0:22:23in the British Army.
0:22:23 > 0:22:26And these men couldn't salute, they couldn't march,
0:22:26 > 0:22:29they didn't know the difference between a tin of bully beef and a brigadier.
0:22:29 > 0:22:33And that sent vibrations of nervousness
0:22:33 > 0:22:35through the corridors of power.
0:22:35 > 0:22:37The old and the bold didn't know how to treat these men,
0:22:37 > 0:22:39they were Royal Engineers now.
0:22:39 > 0:22:4124 hours ago, they'd been sewer drivers.
0:22:41 > 0:22:45Some of them could be trade unionists.
0:22:45 > 0:22:49Even worse than that, some of them could be Scottish trade unionists.
0:22:59 > 0:23:02But military training was of minimal importance.
0:23:02 > 0:23:04The were there to dig,
0:23:04 > 0:23:07to counter the escalating German underground threat.
0:23:07 > 0:23:09That very same evening,
0:23:09 > 0:23:12they travelled to France and within 36 hours,
0:23:12 > 0:23:15Norton-Griffiths had them tunnelling towards the enemy.
0:23:15 > 0:23:20His moles were now the most valuable commodity on the Western front.
0:23:23 > 0:23:25This is the clay-kicking team.
0:23:25 > 0:23:28You've got the kicker here with his kicking iron.
0:23:28 > 0:23:33The bagger, who's passing the lumps of clay back to the trammer,
0:23:33 > 0:23:36who will pass it to somebody else and they will take it out of the system.
0:23:36 > 0:23:38Everything is being done in silence.
0:23:38 > 0:23:40The kicking is done in silence.
0:23:40 > 0:23:42It's not really a kick, it's a push.
0:23:42 > 0:23:44And that's absolutely deliberate.
0:23:46 > 0:23:48Once they've taken out nine inches,
0:23:48 > 0:23:50they put another set of timber in,
0:23:50 > 0:23:53so what you're doing is you're moving towards the enemy
0:23:53 > 0:23:57nine inches at a time, nine inches at a time, nine inches at a time,
0:23:57 > 0:23:59all the way to Berlin almost.
0:24:03 > 0:24:05The men are working in silence,
0:24:05 > 0:24:07they're working in very bad air.
0:24:07 > 0:24:09The rule was if a candle would burn,
0:24:09 > 0:24:11the air was good enough to work in,
0:24:11 > 0:24:15if it went out, you left the tunnel, because there wasn't enough oxygen.
0:24:15 > 0:24:17And they're also searching for the enemy.
0:24:20 > 0:24:25The prime duty of the tunnellers was not offensive, but defensive -
0:24:25 > 0:24:30to protect the infantry in the trenches from being undermined.
0:24:30 > 0:24:33To do so, they had to intercept the Germans
0:24:33 > 0:24:36and turn their galleries into graves
0:24:36 > 0:24:38by blowing them in underground.
0:24:41 > 0:24:44So what you had was listeners at the end of a tunnel like this.
0:24:44 > 0:24:48And the first thing they would use were civilian listening kits.
0:24:48 > 0:24:50This is...
0:24:50 > 0:24:54You stick your ear to it, it's for finding water, leaks.
0:24:54 > 0:24:58So that's the only tool they had at the beginning of the war.
0:24:58 > 0:25:02If they didn't have that, they used this idea.
0:25:02 > 0:25:07Biscuit tin, fill it with water...
0:25:07 > 0:25:09and on the water surface,
0:25:09 > 0:25:16the vibrations of German tunnellers nearby would make that water ripple.
0:25:16 > 0:25:19Now, in November 1915,
0:25:19 > 0:25:21Norton-Griffiths arrived at La Boisselle
0:25:21 > 0:25:23with one of these - the geophone.
0:25:23 > 0:25:28And with it, you could pick up a German tunnelling 100 feet away.
0:25:28 > 0:25:30And you could track them in.
0:25:30 > 0:25:32In chalk, you could pick them out
0:25:32 > 0:25:34260 feet away,
0:25:34 > 0:25:36an extraordinary distance.
0:25:36 > 0:25:42And what that allowed you to do was to track their progress towards you.
0:25:42 > 0:25:44And if they didn't hear you first,
0:25:44 > 0:25:47you could choose the moment that you murdered them.
0:25:54 > 0:25:58In clay, once the decision to blow the enemy had been taken,
0:25:58 > 0:26:02a hole was silently drilled towards the source of the sound.
0:26:02 > 0:26:06Their weapon was a steel tube packed with explosive,
0:26:06 > 0:26:10a terrestrial torpedo known as a camouflet.
0:26:10 > 0:26:13The gallery behind it was then tamped,
0:26:13 > 0:26:18tightly backfilled with sandbags to maximise the explosive force.
0:26:22 > 0:26:26What this conflict has, which no other part of the war has,
0:26:26 > 0:26:29is the ultimate form of barbarism -
0:26:29 > 0:26:33you wait before you blow until you know the maximum number of enemy
0:26:33 > 0:26:36are at the end of that gallery.
0:26:36 > 0:26:38You blow them in, it doesn't matter whether they live or die,
0:26:38 > 0:26:40it doesn't matter to you.
0:26:40 > 0:26:42But then, if you're very clever,
0:26:42 > 0:26:45you've got another charge ready and the one thing you do know
0:26:45 > 0:26:50is that miners will make the maximum effort to save their comrades.
0:26:50 > 0:26:53So you wait for the rescue team to come down,
0:26:53 > 0:26:56wait till they are digging and then, blow them as well.
0:26:58 > 0:27:02In this deadly game, the challenge was to hear and kill the enemy
0:27:02 > 0:27:05before he heard and killed you.
0:27:05 > 0:27:07A race to the death.
0:27:27 > 0:27:30It's funny, cos when you're digging at home,
0:27:30 > 0:27:33you're digging for totally different reasons
0:27:33 > 0:27:35than what you're digging for out here.
0:27:35 > 0:27:41This seems to mean so much more, the rewards are far greater.
0:27:41 > 0:27:45It means something that the men that are out here all the time,
0:27:45 > 0:27:47you know, they'll never go home.
0:27:53 > 0:27:56Norton-Griffiths knew that in sectors like La Boisselle,
0:27:56 > 0:27:58where tunnels were driven through chalk,
0:27:58 > 0:28:01the harder geology demanded different skills.
0:28:01 > 0:28:04So he began to recruit coalminers.
0:28:07 > 0:28:10Norton-Griffiths toured collieries
0:28:10 > 0:28:13asking for men to come forward
0:28:13 > 0:28:16and the men who by and large enlist
0:28:16 > 0:28:19are those who've tried to join the infantry and have been rejected,
0:28:19 > 0:28:24so men who are too old, men in their late 30s, into their 40s,
0:28:24 > 0:28:27and many of them lie about their age.
0:28:27 > 0:28:30The age limit is relaxed, so they'll take men up to 45,
0:28:30 > 0:28:33but there are many even over 45 who were coming forward.
0:28:33 > 0:28:37But the point is that these men are the elite miners,
0:28:37 > 0:28:40they have decades of experience,
0:28:40 > 0:28:43some have been underground since the age of 14
0:28:43 > 0:28:45or even younger for the oldest men.
0:28:45 > 0:28:49And they're highly skilled, they are the aristocracy of the coal mines.
0:28:52 > 0:28:56Tunnelling at La Boisselle now entered a period of intense expansion.
0:28:56 > 0:28:58It was complex and technical
0:28:58 > 0:29:02and required the guidance of an experienced civilian mining engineer.
0:29:02 > 0:29:06Norton-Griffiths insisted he knew the man for the job.
0:29:08 > 0:29:12Norton-Griffiths wrote in his report to the engineering chief
0:29:12 > 0:29:18that 179 Company needed a good strong man.
0:29:18 > 0:29:24And that man that he had in mind was a mining engineer named Henry Hance.
0:29:24 > 0:29:29Now, Hance was described as a first-class rascal.
0:29:29 > 0:29:35But Hance was utterly focused and, it has to be said,
0:29:35 > 0:29:40utterly ruthless in achieving the objectives.
0:29:42 > 0:29:47The tunnellers had a traditional way of letting off steam,
0:29:47 > 0:29:49they were often very fond of drink
0:29:49 > 0:29:52and, in fact, drunkenness was a continual problem
0:29:52 > 0:29:55that affected the efficiency of the tunnelling companies.
0:29:55 > 0:30:00Something that really illustrates the ruthlessness of Henry Hance
0:30:00 > 0:30:04was that where the tunnellers were living,
0:30:04 > 0:30:10there was a boarded-up cellar which was full of wine and brandy.
0:30:10 > 0:30:12And one day, Hance discovered
0:30:12 > 0:30:17that the tunnellers who were living in a cellar
0:30:17 > 0:30:19on the other side of the road to the wine cellar
0:30:19 > 0:30:23had started a tunnel to try to get to it.
0:30:23 > 0:30:27And he went in there with his sergeant major and another officer
0:30:27 > 0:30:33and between them, they smashed every barrel and every bottle in that cellar.
0:30:40 > 0:30:42Hance was a hard man,
0:30:42 > 0:30:47but our excavations show he directed some great feats of engineering.
0:30:47 > 0:30:49Four days of digging exposes a gallery
0:30:49 > 0:30:52marked on military maps as "W Adit".
0:30:52 > 0:30:55It descends to a depth of ten metres
0:30:55 > 0:30:57and contains the remains of a tramway
0:30:57 > 0:31:01employed to shift the vast tonnage of spoil being lifted day and night
0:31:01 > 0:31:02from the deeps below.
0:31:13 > 0:31:17This is W Adit cleaned by our archaeologists.
0:31:17 > 0:31:19Look at the job they've done.
0:31:19 > 0:31:21This is the original floor.
0:31:21 > 0:31:24The gallery is in brilliant condition,
0:31:24 > 0:31:25but when you look at the walls too,
0:31:25 > 0:31:27the candle marks are all still there.
0:31:27 > 0:31:30This was lit by candlelight, of course.
0:31:30 > 0:31:32But what they've revealed on the floor
0:31:32 > 0:31:37is absolutely astonishing, and this is miners' work.
0:31:37 > 0:31:41Here, we've got the original sleepers for the railway,
0:31:41 > 0:31:44we've got the original runners for the railway.
0:31:44 > 0:31:48On top of those would have been too little steel rails
0:31:48 > 0:31:54to run a little wagon from the shaft behind me up to the surface.
0:31:54 > 0:31:56But most remarkable of all,
0:31:56 > 0:32:01is because this thing was not mechanised, it was pushed by hand,
0:32:01 > 0:32:05the tunnellers needed a little bit of help with that and here it is.
0:32:05 > 0:32:09Those holes have been cut by those tunnellers
0:32:09 > 0:32:10to put their feet in
0:32:10 > 0:32:15in order to help them push this heavily-loaded wagon
0:32:15 > 0:32:18up this slope to the surface.
0:32:18 > 0:32:22So I'm walking in the very footsteps of those men,
0:32:22 > 0:32:24even the angle is correct,
0:32:24 > 0:32:28so they can push like a sprinter taking off from the blocks.
0:32:28 > 0:32:32There is nowhere on the Western Front where you can do this,
0:32:32 > 0:32:34except in these tunnels.
0:32:34 > 0:32:36I'm in the footsteps of those men.
0:32:52 > 0:32:55At the end of W Adit is W-Shaft,
0:32:55 > 0:32:58the gateway to a deeper system,
0:32:58 > 0:33:01the fighting levels beneath no-man's-land.
0:33:01 > 0:33:04At first glance, prospects looked good for a descent.
0:33:06 > 0:33:11What I'm doing here is using a mini high-definition digital camera.
0:33:11 > 0:33:14I'm lowering it down.
0:33:14 > 0:33:16There were tunnels going off in that direction,
0:33:16 > 0:33:19and in this direction from this shaft.
0:33:19 > 0:33:23There were tunnellers at the end of listening posts, listening for the Germans,
0:33:23 > 0:33:27and men were working below, infantry were working below helping the tunnellers.
0:33:27 > 0:33:30It's very peculiar sitting here
0:33:30 > 0:33:35knowing what the history of this wall and hole in the ground is.
0:33:39 > 0:33:44By November 1915, Hance's men had dug to 25 metres
0:33:44 > 0:33:47and now began driving their first deep galleries
0:33:47 > 0:33:49out towards the Germans.
0:33:50 > 0:33:52From the right-hand gallery,
0:33:52 > 0:33:57Hance's listeners had detected German picking 15 yards away.
0:33:57 > 0:34:02Hance himself came in and he listened there for six hours
0:34:02 > 0:34:06and he decided they had to blow, so he ordered a chamber to be dug
0:34:06 > 0:34:10to hold 6,000 pounds of ammonal to destroy the German system.
0:34:10 > 0:34:15That was completed at midnight on November 21, 1915.
0:34:15 > 0:34:20And at half past one the following night, the Germans themselves blew
0:34:20 > 0:34:25and it took his charge with their own explosion - and massive blast.
0:34:42 > 0:34:46It was so powerful that the shock came right at the shaft,
0:34:46 > 0:34:49out of the galleries and collapsed one of the entrances.
0:34:49 > 0:34:53The rescue party came down, they brought canaries with them in cages,
0:34:53 > 0:34:55They lowered the canary down to the bottom of the shaft
0:34:55 > 0:34:57and brought it back up two minutes later dead.
0:34:57 > 0:35:00They tried that again and exactly the same thing happened,
0:35:00 > 0:35:02so a man went down in breathing gear
0:35:02 > 0:35:05and he found at the bottom of this very shaft
0:35:05 > 0:35:07which we're looking down now,
0:35:07 > 0:35:11two men dead, gassed. Carbon monoxide gas.
0:35:11 > 0:35:15Using the remains of the winch, which is over there in the corner,
0:35:15 > 0:35:19they lifted their bodies up the shaft and carried them out.
0:35:22 > 0:35:25But two men remained trapped -
0:35:25 > 0:35:28John Lane, 45,
0:35:28 > 0:35:30and Ezekiel Parkes, 37.
0:35:30 > 0:35:34Both coalminers from Tipton, in the Black Country.
0:35:40 > 0:35:44Parkes and Lane are just two of over 120 British and French tunnellers
0:35:44 > 0:35:47who died at the Glory Hole.
0:35:47 > 0:35:50They were simply recorded as "killed in action".
0:35:50 > 0:35:53Perhaps mercifully, families had no inkling
0:35:53 > 0:35:57of the character of their war or the nature of their death.
0:35:59 > 0:36:04Yet, such event could not be a deterrent, work went on.
0:36:04 > 0:36:07We believe the shaft can give us access
0:36:07 > 0:36:09to three kilometres of tunnels
0:36:09 > 0:36:12and a further, even deeper, level.
0:36:12 > 0:36:16We've now cleared the shaft chamber, this is the original shaft chamber.
0:36:16 > 0:36:18And what we're actually doing
0:36:18 > 0:36:22is replacing what the tunnellers put in in 1915 in timber.
0:36:22 > 0:36:24You can still see their original timbers.
0:36:24 > 0:36:26We're replacing that with steel
0:36:26 > 0:36:28and what we're going to do is build a steel cage here
0:36:28 > 0:36:31to protect us from anything that might fall from the roof.
0:36:31 > 0:36:34We'll also use the cage in order to brace this roof,
0:36:34 > 0:36:36cos there's some very severe fractures
0:36:36 > 0:36:38you can see in the rock here.
0:36:43 > 0:36:46And so, the most hazardous part of our exploration begins.
0:36:46 > 0:36:50Over 100 mines shook this chamber from below,
0:36:50 > 0:36:54countless thousands of shells burst above it.
0:36:54 > 0:36:55For a safe descent,
0:36:55 > 0:36:58we need not only a team with many a specialist skill,
0:36:58 > 0:37:01but a structure that will support the technical equipment -
0:37:01 > 0:37:04winches, pumps, cables and ropes.
0:37:11 > 0:37:13As the Somme summer turns to winter,
0:37:13 > 0:37:17we secure the shaft and make it safe to descend.
0:37:22 > 0:37:26All being well, we plan to be the first people for almost a century
0:37:26 > 0:37:30to explore the lower levels of the Glory Hole.
0:37:30 > 0:37:34This really is almost a journey into the Valley of the Kings for us, isn't it?
0:37:36 > 0:37:38Right. OK.
0:37:41 > 0:37:44'For us, as for the tunnellers at the time,
0:37:44 > 0:37:46'the danger from gas is real.
0:37:46 > 0:37:49'Carbon monoxide produced by underground explosions
0:37:49 > 0:37:52'killed as many men as the blasts themselves.
0:37:52 > 0:37:55'Colourless, odourless and lethal,
0:37:55 > 0:37:58'pockets of it may still exist.'
0:37:58 > 0:38:00Put it in front.
0:38:05 > 0:38:10'We may also have other gases to deal with and low oxygen levels.
0:38:10 > 0:38:13'For these are tunnels that haven't been open to the air for many decades.'
0:38:13 > 0:38:15- ..The bottle.- All right.
0:38:23 > 0:38:25Keep the bottle at the back, cos you're going to be...
0:38:27 > 0:38:30'As a precaution, our team have gone through training
0:38:30 > 0:38:32'with equipment made by the same company
0:38:32 > 0:38:35'that manufactured the apparatus supplied
0:38:35 > 0:38:36'to the tunnellers of the Great War.'
0:38:59 > 0:39:00That's it.
0:39:03 > 0:39:06There's a very strong breeze coming through the hole.
0:39:08 > 0:39:09It's clean, clean air.
0:39:09 > 0:39:12We are through, we are through.
0:39:13 > 0:39:15Well done, well done.
0:39:15 > 0:39:19'The air is clear, the shaft stable.
0:39:19 > 0:39:22'Debris still blocks access to the lower levels,
0:39:22 > 0:39:26'but we are able to clear a small hole for a first, brief glimpse.'
0:39:26 > 0:39:29- Yes, you can see the gallery goes away to the left.- Yeah.
0:39:29 > 0:39:33In fact, I think I can see the remains of a wooden railway line.
0:39:35 > 0:39:39The gas detector just slid away into another department.
0:39:45 > 0:39:47- All right?- Yeah.
0:39:47 > 0:39:49Just caught on a knot on your back.
0:39:49 > 0:39:52That's it, just move it... That's better.
0:39:52 > 0:39:54Nice and steady, Pete.
0:39:54 > 0:39:56- OK.- Nice and steady.
0:39:57 > 0:40:00- It's very tight. - How do you feel?- Very tight.
0:40:03 > 0:40:05Very tight indeed.
0:40:05 > 0:40:07- That's enough.- Through there, that's it.
0:40:07 > 0:40:10Does it open up, Pete?
0:40:10 > 0:40:11It's absolutely clear.
0:40:11 > 0:40:13There's railway lines...
0:40:13 > 0:40:15Oh, God!
0:40:15 > 0:40:19It's tiny and it just feels...primeval...
0:40:20 > 0:40:24..primitive, which is precisely what this war was.
0:40:26 > 0:40:27I'll take a photograph.
0:40:33 > 0:40:38Here, finally, are La Boisselle's 25-metre fighting tunnels.
0:40:39 > 0:40:41They give us entry to 11 more shafts
0:40:41 > 0:40:44that descend to the deepest level near the water table.
0:40:48 > 0:40:50'Just a few metres from the foot of W-Shaft,
0:40:50 > 0:40:52'is the end of the gallery
0:40:52 > 0:40:54'in which John Lane and Ezekiel Parkes were working
0:40:54 > 0:40:58'on the night of 22 November 1915.'
0:40:58 > 0:41:00And just up ahead here...
0:41:02 > 0:41:05..is a place I've been rather nervous of seeing.
0:41:06 > 0:41:09Here is the blocked gallery
0:41:09 > 0:41:13where Ezekiel Parkes and John Lane still lie.
0:41:17 > 0:41:18It's a grave.
0:41:21 > 0:41:24But we need to pay our respects.
0:41:26 > 0:41:29We're the first people down here in 95, 97 years.
0:41:29 > 0:41:31They need to know we're here.
0:41:33 > 0:41:36And they need to know that we know they are still here.
0:41:44 > 0:41:50In early 1916, plans were laid for a major summer offensive on the Somme.
0:41:50 > 0:41:52It was to present Hance's tunnellers
0:41:52 > 0:41:55with their greatest challenge of the war.
0:41:55 > 0:41:58Instead of simply offering protection,
0:41:58 > 0:42:02they were now to play a key role in spearheading the attempt
0:42:02 > 0:42:04to break two years of stalemate.
0:42:07 > 0:42:10The French had thrown themselves at the German bull.
0:42:10 > 0:42:15They'd lost hundreds of thousands of men and gained nothing at all.
0:42:15 > 0:42:21And come 1916, with the Battle of Verdun going on,
0:42:21 > 0:42:25which was designed to bleed France white.
0:42:25 > 0:42:28That was the German goal - to bleed France white,
0:42:28 > 0:42:31and force a political solution.
0:42:32 > 0:42:35Then, came the turn of the British
0:42:35 > 0:42:37in Picardy, on the Somme,
0:42:37 > 0:42:41with French help, they were going to break this barrier
0:42:41 > 0:42:43and force open warfare.
0:42:43 > 0:42:44Smash the Western Front
0:42:44 > 0:42:49and that is where La Boisselle came in.
0:42:49 > 0:42:53Because this was in the epicentre of that planned battlefield
0:42:53 > 0:42:55the Albert-Bapaume road
0:42:55 > 0:42:59was THE main axis of Allied attack,
0:42:59 > 0:43:01for this great battle of the Somme.
0:43:05 > 0:43:07The village was German property.
0:43:07 > 0:43:10It was impossible to attack it frontally
0:43:10 > 0:43:11because of the crater field
0:43:11 > 0:43:14and because it was bristling with weapons.
0:43:14 > 0:43:17So the plan was to obliterate the German front lines
0:43:17 > 0:43:19either side of it with artillery.
0:43:19 > 0:43:24The tunnellers' job was to plant two huge mines on either flank.
0:43:24 > 0:43:26On this side, Y-Sap,
0:43:26 > 0:43:30and on the far side, Lochnagar.
0:43:30 > 0:43:33That would blow a hole in the German defences,
0:43:33 > 0:43:35which they could not defend.
0:43:35 > 0:43:39And through those two holes would swarm the infantry.
0:43:41 > 0:43:45Both mines were 179 Tunnelling Company's responsibility.
0:43:46 > 0:43:48The 320-metre Y-Sap tunnel
0:43:48 > 0:43:51was driven from the deep level near the cemetery.
0:43:53 > 0:43:57Its purpose - to eliminate a multiple machine-gun position
0:43:57 > 0:43:59on the north flank of the village.
0:44:03 > 0:44:06'Mining efforts at the Glory Hole were redoubled
0:44:06 > 0:44:08'in the months leading up to the attack.
0:44:08 > 0:44:11'As the tunnellers inched their way towards the objectives,
0:44:11 > 0:44:14'anticipation was mixed with fear
0:44:14 > 0:44:17'were they about to deliver a knockout blow
0:44:17 > 0:44:20'or would the Germans hear them and blow them up first?'
0:44:22 > 0:44:24Timber been cut into the sidewall here.
0:44:24 > 0:44:28Just to give them a little bit of extra protection.
0:44:34 > 0:44:38Try to imagine, which we can't, of course,
0:44:38 > 0:44:42a German blow taking place near here.
0:44:42 > 0:44:45This wall would simply crush you against that wall
0:44:45 > 0:44:47with the force of it.
0:44:47 > 0:44:52You can see the ground has been shattered. That is from...
0:44:52 > 0:44:55That's from German and British mine blows.
0:44:55 > 0:44:58Shattered ground.
0:44:58 > 0:45:00But it's still holding up.
0:45:00 > 0:45:04What would you do in a place like this if there was an emergency?
0:45:04 > 0:45:07If the Germans blew a mine and all those men...
0:45:07 > 0:45:11There were 900 people working underground here.
0:45:11 > 0:45:14How on Earth would you reach the shaft?
0:45:14 > 0:45:16What a scramble that would be.
0:45:18 > 0:45:19Oh, the horror of it.
0:45:24 > 0:45:28I found the other shaft chamber, here, just on my left-hand side.
0:45:28 > 0:45:30You might be able to hear the echo?
0:45:30 > 0:45:32HE CHUCKLES
0:45:32 > 0:45:35It's perfectly cut, as you would expect.
0:45:35 > 0:45:36And that goes further on.
0:45:36 > 0:45:39It goes on and on and on, I can't see the end of the gallery.
0:45:39 > 0:45:43And off it are the listening posts and the mine chambers.
0:45:43 > 0:45:46Off in the direction of the enemy.
0:45:46 > 0:45:48In that easterly direction.
0:45:50 > 0:45:53'Laying a mine isn't just about digging tunnels.
0:45:53 > 0:45:58'It involves the excavation of underground caverns, mine chambers,
0:45:58 > 0:46:00'to house the explosive charge.
0:46:01 > 0:46:06'Once filled, the gallery behind was packed with sandbags of chalk
0:46:06 > 0:46:08'to force the blast vertically.'
0:46:11 > 0:46:13This is the entrance to a mine chamber.
0:46:13 > 0:46:16There's a tunnel going out under no-man's-land,
0:46:16 > 0:46:19cos we are under no-man's-land here.
0:46:19 > 0:46:22And it goes forward and zigzags and there's a chamber at the end of it.
0:46:22 > 0:46:25This bit has been blocked up, probably just backfill.
0:46:25 > 0:46:27But I can see beyond.
0:46:27 > 0:46:29But I've just seen something very,
0:46:29 > 0:46:32very thought-provoking indeed,
0:46:32 > 0:46:33because down here...
0:46:36 > 0:46:38..are the cables for the mine.
0:46:39 > 0:46:41They've been cut, fortunately.
0:46:43 > 0:46:46But what we don't know, of course,
0:46:46 > 0:46:48is whether there's still a mine in there.
0:46:50 > 0:46:52What a very strange thought.
0:47:00 > 0:47:03By early summer, excellent progress had been made.
0:47:03 > 0:47:05But now, the galleries had to pass
0:47:05 > 0:47:08beneath a belt of suspected German listening posts.
0:47:08 > 0:47:11A new approach was required.
0:47:11 > 0:47:14There were times when you were mining,
0:47:14 > 0:47:17when there was no choice, but to work with noise.
0:47:17 > 0:47:19However, when it came to the big mines,
0:47:19 > 0:47:23which were being prepared for the beginning of the battle, Lochnagar and Y-Sap,
0:47:23 > 0:47:26everything had to change when they reached a certain point.
0:47:26 > 0:47:31The pick was put down in favour of the bayonet.
0:47:31 > 0:47:35It was a little bit like a clay-kicking team, in fact.
0:47:35 > 0:47:37One man with the point of his bayonet
0:47:37 > 0:47:40just easing out a lump of chalk,
0:47:40 > 0:47:41the second man catching it,
0:47:41 > 0:47:43but the third man was an officer
0:47:43 > 0:47:45and his job was to make sure
0:47:45 > 0:47:48that those first two worked in the maximum amount of silence.
0:47:52 > 0:47:57High Command finally selected 29th of June as the day of the attack,
0:47:57 > 0:48:01to be preceded by the greatest artillery onslaught in history.
0:48:03 > 0:48:07But completing Lochnagar by bayonet alone proved impossible,
0:48:07 > 0:48:10the tunnel was stopped short
0:48:10 > 0:48:15and two huge chambers dug to hold 60,000 pounds of explosive.
0:48:15 > 0:48:18By far, the biggest British charge of the war to date.
0:48:24 > 0:48:28The preliminary bombardment began on the 24th of June.
0:48:28 > 0:48:32Over the next week, a torrent of 1.7 million shells
0:48:32 > 0:48:35descended upon the Germans.
0:48:35 > 0:48:39The countdown to the tunnellers' moment of glory was under way.
0:48:43 > 0:48:46Hance had charged his men to plant 20 tonnes of explosives
0:48:46 > 0:48:48beneath the Y-Sap.
0:48:48 > 0:48:5030 tonnes beneath Lochnagar.
0:48:50 > 0:48:53And two enormous charges under the Glory Hole itself,
0:48:53 > 0:48:56to destroy the German tunnel system.
0:48:56 > 0:48:59The bombardment was falling. Time was running out.
0:48:59 > 0:49:02There was no more tension than at this moment.
0:49:02 > 0:49:06Through these fields were lines and lines of infantrymen
0:49:06 > 0:49:10carrying tins of ammonal explosives up to the mines, up to the chambers,
0:49:10 > 0:49:13to charge them, ready for the first of July.
0:49:13 > 0:49:15Nerves were at breaking point.
0:49:27 > 0:49:29Even 100 years later,
0:49:29 > 0:49:33these front-line German trenches are still two metres or more deep.
0:49:33 > 0:49:36This is what the British had to contend with.
0:49:36 > 0:49:38Henry Hance had an idea for this.
0:49:38 > 0:49:41He wanted to blow Y-Sap early, several days early,
0:49:41 > 0:49:44so it would wipe out the German machine-gun positions
0:49:44 > 0:49:46and also shorten the distance
0:49:46 > 0:49:49that the British troops would have to attack across no-man's-land.
0:49:52 > 0:49:55The resulting crater, he said, could then be occupied
0:49:55 > 0:49:58and employed to dig an advanced jumping-off trench
0:49:58 > 0:50:00for the British infantry,
0:50:00 > 0:50:03a trench that would effectively reduce the distance
0:50:03 > 0:50:06across no-man's-land by over 150 metres.
0:50:10 > 0:50:15What Henry Hance was trying to achieve by blowing up Y-Sap early
0:50:15 > 0:50:19was to cut out the German chance of enfilade.
0:50:19 > 0:50:22And that means firing the machine guns up no-man's-land,
0:50:22 > 0:50:26along no-man's-land, at about knee height.
0:50:26 > 0:50:28If you just trained your machine gun and fired it,
0:50:28 > 0:50:31it meant that the British troops crossing this way
0:50:31 > 0:50:34would have to walk through a stream of bullets
0:50:34 > 0:50:39and they would be cut off at the legs, and when we talk about men being cut down like a scythe,
0:50:39 > 0:50:42that's what happened with machine guns.
0:50:42 > 0:50:44They were just cut down here and fall to the ground.
0:50:47 > 0:50:49Hance's core commander agreed
0:50:49 > 0:50:53that neutralising enemy fire from the flanks would save lives around La Boisselle,
0:50:53 > 0:50:58but the explosion would warn the enemy an infantry attack was imminent.
0:50:58 > 0:50:59So the answer was no.
0:51:03 > 0:51:06'As the big day drew close, the attack was delayed.
0:51:06 > 0:51:10'British commanders were most anxious that the actual moment of assault,
0:51:10 > 0:51:16'now set for 7.30am on the first of July, should not be compromised.
0:51:16 > 0:51:20'But it was compromised, and it happened here, at La Boisselle.'
0:51:21 > 0:51:25Mine chamber. An uncharged mine chamber.
0:51:27 > 0:51:28But also a listening post.
0:51:33 > 0:51:36What the British were not aware of until after the battle
0:51:36 > 0:51:38is something rather serious.
0:51:38 > 0:51:43In fact, possibly the most serious but little-thought-of fact,
0:51:43 > 0:51:47and that was that in one of the German tunnels, there was a chamber,
0:51:47 > 0:51:51within which was a machine called a Moritz system.
0:51:53 > 0:51:56And it was specially designed to pick up electrical impulses
0:51:56 > 0:51:58passing through the earth itself.
0:52:00 > 0:52:02Telephone impulses.
0:52:02 > 0:52:06And somebody on the British side on the night of the 30th of June
0:52:06 > 0:52:10sent a telephone message, unscrambled,
0:52:10 > 0:52:12to one of the brigades holding the line here.
0:52:12 > 0:52:16And it said, "Good luck tomorrow morning."
0:52:18 > 0:52:22The only thing the Germans did not know after eight days of bombardment
0:52:22 > 0:52:25was the moment of the British attack
0:52:25 > 0:52:28and the British had just told them.
0:52:36 > 0:52:39The first of July was a clear, warm day
0:52:39 > 0:52:42but the air trembled with the thunder of artillery.
0:52:44 > 0:52:47The infantry were poised to go into action,
0:52:47 > 0:52:51all mines charged and exploders connected.
0:52:51 > 0:52:53After months of toil,
0:52:53 > 0:52:57the tunnellers were prepared and ready for their moment.
0:53:00 > 0:53:02These trenches filled with infantry.
0:53:03 > 0:53:06They knew nothing at all of what was going on beneath their feet.
0:53:06 > 0:53:09They were not allowed to know that.
0:53:09 > 0:53:11Because if they'd been captured with that information,
0:53:11 > 0:53:14it could have led to the loss of those mines.
0:53:14 > 0:53:18The tunnellers were ready to push the plunger down.
0:53:18 > 0:53:20That was their moment of no return.
0:53:20 > 0:53:25For the infantry, however, it was this, it was this sound.
0:53:25 > 0:53:30That's when they knew they were going over the top.
0:53:33 > 0:53:367.28 two minutes to zero.
0:53:40 > 0:53:45The scale of the eruptions was most dramatically seen from the sky.
0:53:45 > 0:53:48Aerial observer Cecil Lewis had a unique view.
0:53:49 > 0:53:53"There was an ear-splitting roar, drowning all the guns,
0:53:53 > 0:53:57"flinging the machine sideways in the repercussing air.
0:53:57 > 0:54:02"The earthly column rose, higher and higher to almost 4,000 feet.
0:54:02 > 0:54:06"There it hung or seemed to hang for a moment in the air.
0:54:06 > 0:54:09"Like the silhouette of some great Cyprus tree."
0:54:18 > 0:54:22This is the extraordinary result of 30 tonnes,
0:54:22 > 0:54:2460,000 pounds of explosive.
0:54:24 > 0:54:26Everything in the path of this crater
0:54:26 > 0:54:29would have been simply obliterated.
0:54:29 > 0:54:31And finally, the shock wave from this massive explosion
0:54:31 > 0:54:35passed through the German dugout, through the soldiers themselves,
0:54:35 > 0:54:37haemorrhaging their brains.
0:54:42 > 0:54:47Two minutes later, troops from the Tyneside Scottish and Tyneside Irish
0:54:47 > 0:54:49rose to assault enemy trenches
0:54:49 > 0:54:52that lay smoking and pulverised before them.
0:54:52 > 0:54:54But something wasn't right,
0:54:54 > 0:54:58in Mash Valley, next to the huge Y-Sap crater,
0:54:58 > 0:55:01the leading waves were seen to wither and fall
0:55:01 > 0:55:04before they had gone 100 metres.
0:55:04 > 0:55:09The Germans had heard British tunnelling, evacuated Y-Sap,
0:55:09 > 0:55:11installed their machine guns elsewhere
0:55:11 > 0:55:14and throughout no-man's-land produced a lethal hail
0:55:14 > 0:55:16of enfilade cross-fire.
0:55:18 > 0:55:21Hance's worst nightmare had come true.
0:55:24 > 0:55:26The Germans were not neutralised
0:55:26 > 0:55:28and that's because the Germans were in dugouts,
0:55:28 > 0:55:31deep shelters underneath the trenches.
0:55:31 > 0:55:34They'd taken their weapons down there,
0:55:34 > 0:55:36the moment the bombardment stopped or moved on,
0:55:36 > 0:55:39up they came out of the dugout,
0:55:39 > 0:55:41placed their machine guns on the parapets
0:55:41 > 0:55:44and cut down the British soldiers, like corn.
0:55:44 > 0:55:47They were scythed down like corn.
0:55:47 > 0:55:535,100 men lay in this valley before noon on the first of July.
0:55:57 > 0:55:58On the other side of the village,
0:55:58 > 0:56:01in Sausage Valley, where Lochnagar was blown,
0:56:01 > 0:56:05over 6,000 men were dead, wounded and missing.
0:56:06 > 0:56:08The killing fields astride the Glory Hole
0:56:08 > 0:56:10saw the highest concentration of casualties
0:56:10 > 0:56:14on the entire Somme battleground that day -
0:56:14 > 0:56:17the most disastrous in British military history.
0:56:19 > 0:56:23La Boisselle was meant to have fallen within 20 minutes.
0:56:23 > 0:56:26That night, it was still in German hands.
0:56:27 > 0:56:31Their two-year occupation had allowed them to create a bastion
0:56:31 > 0:56:36with hundreds of deep shelters that withstood the pummelling of even the heaviest British guns.
0:56:38 > 0:56:44And so, the tunnellers had achieved everything...and nothing.
0:56:44 > 0:56:49The fact that it did not help the infantry was not their fault.
0:56:49 > 0:56:53British High Command had put their faith in the guns,
0:56:53 > 0:56:56that was the major weapon in their armoury.
0:56:56 > 0:56:59But the Germans knew that, they had prepared.
0:56:59 > 0:57:04And they put themselves underground out of harm's way.
0:57:04 > 0:57:08So, at La Boisselle, the tunnellers did everything in their power
0:57:08 > 0:57:11to assist the infantry to succeed,
0:57:11 > 0:57:13but it was never going to be enough.
0:57:17 > 0:57:19What happened on the first of July
0:57:19 > 0:57:21exposed the limitations of mine warfare.
0:57:23 > 0:57:28It can deliver destruction, shock and awe on a grand scale,
0:57:28 > 0:57:30but only momentarily.
0:57:32 > 0:57:36When La Boisselle finally fell to the British on the fourth of July,
0:57:36 > 0:57:39the Glory Hole became immediately redundant,
0:57:39 > 0:57:42abandoned as the front line crept forward.
0:57:44 > 0:57:47No tunneller can keep up with a moving army.
0:57:48 > 0:57:53Along the old Roman road, the battle continued until mid November,
0:57:53 > 0:57:56claiming a further million casualties
0:57:56 > 0:57:59for six miles of bludgeoned terrain.
0:58:00 > 0:58:05Today, agriculture shares the fields and pastures of the Somme
0:58:05 > 0:58:07with monuments to the fallen.
0:58:09 > 0:58:12Little survives of the surface war,
0:58:12 > 0:58:16but beneath lies the kingdom of the tunnellers.
0:58:16 > 0:58:19The world they made at such great cost
0:58:19 > 0:58:23and where so many remain entombed is all still there.
0:58:23 > 0:58:26This is their monument.
0:58:54 > 0:58:57Subtitles by Red Bee Media Ltd