The attempt to tunnel out of Stalag-Luft 3 was one of the most audacious episodes of the Second World War, immortalised in the movie The Great Escape. Seventy Allied prisoners toiled for months to get out of the German camp, but only three made it to freedom and 50 were executed as punishment for trying.
Now the only remaining tunnel of the three they dug, codenamed Dick, has been found and excavated by archaeologists after lying undisturbed for six decades.
The other two routes, Harry - through which the actual escape took place - and Tom, were collapsed when discovered by the German Luftwaffe who ran the camp.
Dick, which was abandoned before completion, remained untouched.
Now, on the 60th anniversary of the escape on 24 March 1944, two archaeologists, Peter Doyle from Britain and Larry Babits from the US, accompanied by three of the few surviving prisoners who worked on the tunnel, have rediscovered Dick at the abandoned and overgrown site of the camp near Zagan in modern-day Poland.
Survivors of the "Great Escape" watched the excavation team - filmed by a documentary crew for broadcast this week - uncover the tunnel and unearth a treasure trove of artefacts, such as makeshift lamps made from powdered milk tins and mutton fat, as well as ventilation pipes. They also found stamps carved from the rubber heels of flying boots which were used to forge documents for escapees.
RAF pilot Bertram "Jimmy" James, who escaped 10 times before he was placed in Stalag-Luft 3 and is one of only seven escapees who is still alive, said yesterday: "It was a very moving experience and also very strange to see a great big hole humming with diggers, archaeologists, film crews and God knows what else.
"I never thought I would go back to see the tunnel and it brought back the ghosts from the past, all the friends who were shot."
Mr James, 88, who worked for many years in the diplomatic service and retired to live in Ludlow, Shropshire, said: "I'm not entirely surprised it was so well preserved. It is very dry underground and it was fossilised to some extent. I think if it had been damp it would have gone. On the whole, the film was pretty accurate but the motorbike chase was pure Hollywood fantasy."
More than 10,000 Allied prisoners were held at Stalag-Luft 3, a maximum-security camp designed to deter any escapes that was sited on sandy ground to make tunnelling more difficult.
Alan Bryett, an RAF bomb aimer before he was captured and placed in the camp, said: "The desire to get out was a very strong one because you realised this was going to be your prison for an unknown length of time. This was the end of life, really. That's the thing that horrified me more than anything."
Another tunneller, Walter Morrison, said attempting to escape was "a game, a sport". "It was more like a traditional English field sport in its way. It was played by the rules - you must not use violence, you must not engage in sabotage or espionage if you're outside the camp, and if you get caught you must spend two weeks in the cooler in solitary confinement - not a very serious penalty."
Work began on the tunnels in early 1943 with their concealed entrances completed by April of that year. Harry was under a stove, Tom in the corner of a dark corridor and Dick was in the drainage sump of a washroom.
Using handmade tools, the prisoners dug 30 feet down before heading horizontally towards the camp perimeter. They scavenged pieces of wood to support the tunnel along its length and prevent collapse of the unstable sand. Around 4,000 boards from the prisoners' bunks, 34 chairs and 52 tables were requisitioned for the purpose.
A makeshift ventilation system was constructed to combat the lack of oxygen underground.
But as work progressed, Dick was sacrificed to store materials for the escape - fake documents, uniforms and civvies - and to hide the excavated sand from the other tunnels.
The Germans eventually stumbled across Tom, but they were so pleased with their find, which they demolished, that they failed to look for other escape routes.
The escape bid eventually took place on a moonless night to lessen the chances of being spotted. But when the first escapee, Johnny Bull, came to the surface he found to his horror that the exit was 15 feet short.
The tunnel, which had taken a full 10 minutes to negotiate, emerged in a clearing beyond the perimeter fence rather than in the nearby forest which the plotters had hoped would hide their movements.
The plan was for as many as possible to get out, even if they only managed to get five miles before being caught.
"It would confuse the Germans as to how many had got out, while the real escapers who went by train were really making their proper escapes," Mr Bryett said.
But the slow progress, as prisoners timed their exit to avoid the sweep of searchlights, meant that just 76 got out before the Luftwaffe rumbled the plan. Only three of the escapees - two Norwegians and one Dutchman - reached safety. The rest were rounded up and 50 were executed - an outrageous act that later led to war crimes tribunals.
"Jimmy" James made it to the Czech border but was caught and put in another camp until the end of the war. While visiting the site of the tunnel, he went to see a nearby memorial to the 50 men who were killed. "You think, 'why isn't my name up there?'" he said. "It's just luck, the fortune of war."
The documentary on "The Great Escape" will be broadcast on Channel 5 on Wednesday at 9pm