Somme gives up its secrets

When an archaeologist found fragments of human bone, a hush descended on the dig outside a sleepy village in Northern France.

The team members have got used to this experience. They are after all working at a site which was part of the Somme battlefields and witness to some of the bloodiest fighting in military history.

Iain McHenry is one of the founding members of the La Boisselle Study Group - an Anglo-French band of military historians excavating a plot of private land which straddled the Allied and German trenches during World War One.

''It is always a great leveller when you come across human remains,'' he said. ''You know we are only 100 years or so since the event so there are family members present still.''

Iain explained that the hardest task is identifying the remains they find. Sadly many troops were blown apart by shells, and by explosions set off by German tunnellers. In this case, though, the team met with success.

''We found an identity disc'', he said, ''alongside a uniform button and unfired bullets. His name was Francois Bideau. He was an infantry soldier with the 118th Battalion of the French infantry which recruited from the Brittany area of France.''

On the day I was visiting the news came through that Pvt Bideau's family had been contacted and told of the news.

The team has been granted access to the site by the landowners, a family keen for the world to learn more about the area and those who fought so bravely there.

What makes the site fascinating is that this is where trench warfare on the Western Front began; French and later British soldiers dug in just before Christmas 1914 and stayed put until the first day of The Somme offensive on July 1st 1916.

It was the bloodiest fighting on record for the British Army - 57,000 soldiers killed or wounded on the first day alone.

Among the troops serving here, men from the 1st Dorsetshire regiment. They took heavy losses raiding a German position known as Y-Sap on March 26th 1916 under cover of a mine explosion.

And that brings us to the really extraordinary aspect of the dig - the re-discovery of what could be many miles of British tunnels.

Scooped out of chalk they run under the Allied trenches. As they were being made the Germans were digging too...each side would plant explosives, trying to blow each other up.

There were more than 100 recorded explosions here during the war - the remnants of them can be seen in the form of dozens of craters still dotting the landscape.

As we journey into the parts of the tunnel which have been excavated, historian Jeremy Banning says: ''When we first came in here it was full of spoil that had slid in, this was our main way into the tunnel system. There was a slow collapse so we worked our way down - this has all been cleared out now. Much more claustrophobic when we originally came down here.''

The Dorsets and the other soldiers in the trenches likely knew very little about what was going on down below. Some troops did, though. There are records showing that Essex servicemen were drafted in to help with the constant digging, bucketing and barrowing chalk out of the tunnels.

We come to the bottom-most part that people can visit. It's thirty foot down but the team has already tapped into a shaft which plummets another fifty feet

Kent First World War historian and project director Peter Barton uses a rake to illustrate the scene below us, the part of the network which has yet to be explored.

''When you get down to the bottom of this shaft you have this shape,'' he says. ''Imagine that is the shaft, the rake at the bottom you have galleries going off horizontally, and then in front of that you have other tunnels going out. It's just like a rake. And each of these tunnels you have either got somebody listening for the Germans tunnelling the other way or a mine chamber, so it's effectively an underground submarine net to stop the Germans undermining your own trenches.''

The tunnellers themselves were mainly miners from all over the British Empire. They had little or no military training. They took their orders directly from mining engineers who were in turn given objectives by military men. The strategy appears to have been to undermine the German tunnelling and to cause as many explosions as possible under enemy lines.

Jeremy Banning said: ''Any movement, any sound you made was picked up potentially by a German who may be that far away, or maybe ten foot away. You can't see. And so this could be your last breath, your last movement. That experience, how can we experience what that was like? It must have been a totally terrifying kind of war.''

The study group began work in the Summer of 2011 and carries out digs as and when manpower can be mustered and funds raised. Members hope to uncover much more of the network and spend many more years investigating this poignant piece of military history.

As for the miners, many died of course. From explosions, from the rigours of the work and even in battle. They would sometimes dig into a German section of tunnel and a gunfight or hand-to-hand combat would break out.

Were their efforts and sacrifice worth it?

''They were indispensable'', Peter Barton said. ''You cannot divide the surface war from the underground war. The trenches were protected by these men but the infantry knew nothing about it, they weren't allowed to. They were utterly essential to protect that trench line.''

For more information about the project, visit the group's website here.

Human remains and soldiers' equipment have been found.