By Robert Hall
BBC News, Belgium
Ninety years after the battle of Passchendaele, officially known as the third battle of Ypres, a group of enthusiasts is attempting to dig up some of the key trenches of World War I.
Conditions at the front were horrendous for troops
Across a flat, muddy Flanders landscape, a solitary figure is plodding along the furrows.
Geophysicist Malcolm Weale is a battlefield detective who specialises in uncovering history that has lain hidden for generations.
In this case, the ground beneath his feet shields secrets of World War I.
The farmland near the Belgian village of Zonnebeke was criss-crossed by the trenches that saw horrendous loss of life - the whining of Malcolm's equipment betraying the metal fragments of shells and equipment turned up by the ploughs every spring.
But Malcolm and the archaeologists who called him in are looking for one particular piece of history.
Somewhere nearby is a remnant of the hidden war - the shelters and deep bunkers that protected troops from the hail of explosive.
During the height of the campaigns around Ypres, tens of thousands of men spent much of the lives underground.
Held by the Allies until the 1918 German offensive, briefly occupied by German forces, recaptured by the British at the end of the war
Units that operated there:
100 Brigade, 33rd Division
16th King's Royal Rifle Corps
9th Battalion Highland Light Infantry Regiment
2nd Battalion Worcestershire Regiment
The men leading this search have spent years delving into the history of these tunnels, and the engineers who dug them.
Peter Barton, a British historian, has written several books on the subject.
Johann Vandewalle, who lives nearby, has been fascinated by this little known aspect of the war since he discovered his first tunnel as a child.
Working from the original trench maps, they have identified a tunnel known as the Vampire Dugout - a brigade headquarters that would have housed a senior officer and up to 50 men.
Constructed 90 years ago by the British during the Battle of Passchendaele, the shelter was later captured by the Germans.
Flooded, buried and forgotten after the war, it has not been entered in nine decades.
Malcolm Weale has used latest technologies for warfield clues
Malcolm's radar has identified underground objects and structures that suggest the Vampire Dugout has been rediscovered.
The next stage will be to remove a layer of topsoil, then to begin digging by hand towards the stairwells that lead some 40ft (12m) below the old trench system.
The tunnels themselves will be full of water, and that's what excites the archaeologists.
Lack of light and oxygen will mean that anything left in the dugout is perfectly preserved - beds, weapons, clothing, and personal possessions have all been recovered by previous, more modest excavations.
Standing with the team under drizzly Belgian skies I could sense their excitement, and a degree of tension.
The farmer who owns the land needs to plant his crop within a few weeks - the clock is ticking, but if hunches are correct, we could be digging in the next few days.
The historians want to find out what everyday trench life was like
Johann tried to describe his emotions: "You can read about the war in books, or learn from pictures, but here we will actually touch, and smell that history.
"No-one has walked in these tunnels since the battle. We will get a real sense of what daily routine was like."
Next week, if all goes according to plan, we will provide the first live images of that moment - tiny cameras will travel into the tunnels with the historians, as they pick their way into the darkness.
Their hope is that the items they find will provide clues to the units that served here, and eventually to the personal stories of individual soldiers.
A fascinating way of bringing the past to life - and perhaps reconnecting families to those they lost so long ago.