This is not some Hollywood movie - this is the real thing. The third of this weekend's programmes about tunnels follows three ex-PoWs as they track down the entrance to "Harry", the tunnel they and 73 other RAF officers used to escape from Stalag Luft III during the Second World War.
It was an extraordinary undertaking. Five hundred officers were involved in the planning, security, tailoring, document forging, digging and underground railway construction.
Only three men got home safely. The rest were recaptured and 50 were shot by the Gestapo. After this, escapes were, in the words of the German propagandists, "no longer a sport".
Director Chris Rawlence
Executive producer John Triffitt
A Hauer Rawlence production for BBCtv
(The Wooden Horse at at 11.30pm is also part of the Going Underground season)