Not since the 1970s has there been such an important discovery from the Great War in France. In woods on a ridge not far from the city of Reims, the bodies of more than 270 German soldiers have lain for more than a century - after they died the most agonising deaths imaginable. Forgotten in the confusion of war, their exact location was till now a mystery - one which the French and German authorities were in no hurry to elucidate. But thanks to the work of a father-and-son team of local historians, the entrance to the Winterberg tunnel on the Chemin des Dames battlefront has been found. The urgent question is what to do next. Should the bodies be brought up quickly and buried in a German war cemetery? Should there be a full-scale archaeological dig so we can learn more about the conduct of the war and the lives of the men who fought it? Should there be a memorial, or a museum? The two governments are still deliberating, but time presses. Because if the tunnel's location is in theory still a secret, it is a secret that has been badly kept. When I visited the spot a few days ago, it was to discover that bounty-hunters had been the night before. A three-metre deep hole had been dug near the entrance, and a collection of wartime artefacts - axes, spades and pit-props as well as unexploded shells - left in a heap. We also found a human ulna - the fore-arm bone. The looters had not managed to break into the tunnel - that lies even deeper down - and what they found are bits and pieces thrown up in the shell explosion that sealed it off. But no-one doubts they will be back, because whoever gets into the Winterberg tunnel first will find a treasure trove. In the spring of 1917 the French launched a doomed offensive to retake the hills that lie in a west-east line a few miles to the north of the river Aisne. The Germans had held the crest along the Chemin des Dames for more than two years, and they had a complex system of underground defences. Near the village of Craonne, the Winterberg tunnel ran for 300m from the north side of the crest - invisible to the French - and came out to supply the first line of German trenches on the south-facing slope. On 4 May 1917 the French launched an artillery bombardment targeting the two ends of the tunnel, sending up an observation balloon to get a sight on the north-facing slope. For once their accuracy was formidable. A shell fired from a naval gun hit the entrance, triggering more explosions from ammunition that was stored there and sending a cloud of acrid fumes into the shaft. Another shell sealed the exit. Inside, the men from the 10th and 11th companies of the 111th Reserve Regiment were trapped. Over the next six days, as oxygen ran out, they either suffocated or took their own lives. Some asked comrades to kill them. By a fluke of physiology, three men survived long enough to be brought out by rescuers, just a day before the crest was abandoned to the French. One of them, Karl Fisser, left an account for the regimental history: "Everyone was calling for water, but it was in vain. Death laughed at its harvest and Death stood guard on the barricade, so nobody could escape. Some raved about rescue, others for water. One comrade lay on the ground next to me and croaked with a breaking voice for someone to load his pistol for him." When the French took the ridge, the scene outside would have been of untold chaos and destruction. Digging into the tunnel would hardly have been a priority, so they left it. The Germans retook the Chemin des Dames in a later push, but at that point they had no time either to search for remains.