Forty feet below the fields in Northern France hides a secret history, one that dates back more than a hundred years.
Tunnels were first dug during the First World War to mine under enemy positions and detonate bombs or attack in desperate and fierce fights.
But as the war dragged on, they developed another purpose: providing soldiers with safer accommodation and communication routes.
Miners and engineers from Britain and Australia began tunnelling near Hulluch in 1916 in the wake of the Battle of Loos.
Lt Col (Retd) Phillip Robinson, The Durand Group said:
“In 1918 these were all interlinked and it was possible to walk underground from the La Bassée canal, about 6km [away], all the way down to here.
“Troops were accommodated in there but in particular it provided safe passage for the troops.
“Call them underground communications trenches, off which you then had all the dugouts and rest of it.”
A team of former military personnel, tunneling engineers, bomb disposal operators and archaeologists is now restoring the subway system and giving valuable insight into underground warfare.
The Durand Group have big plans for the tunnels and the 3km they have uncovered bring an unseen part of First World War history to light.
Soldiers did not live in the tunnels permanently, but they would often work underground for several days at a time.
First World War graffiti remains engraved on the tunnel walls, acting as an insight into the soldiers’ lives who served there.
Maj (Retd) Andy Hawkins QGM MBE, The Durand Group said: “You’ve probably got several hundred men operating and living down here all the time, so you have that sweat and effort going on.
“Of course, in the living areas they would have had latrines, there were cookhouses down here as well so there would have been cooking smells.
“Plus that constant risk of artillery fire coming in so the whole thing would vibrate… dust.”
In 1940, the tunnels were used again when a redesign was started for a corps headquarters, before being abandoned due to the advancing German forces.
Having painstakingly restored much of the tunnels, the Durand Group now want to invite people in to walk more than a kilometre underground.
The Loos Big Walk is a 26-kilometre route across, and under, the battlefields of the Western Front proposed by the Durand Group for interested members of the public.