The Gibraltar chamber had the innocuous name of the “Stay Behind” Cave. But this was no game. This was a top-secret wartime mission, code-named Operation Tracer, in which six men volunteered to be buried alive in the cave if the Rock were captured by the Germans, so they could continue to monitor enemy movements.
The team were warned before they left for Gibraltar that they may have to be sealed inside the operation post for as long as a year, although they were aware that it could be longer. The operation was so secret that not even Whitehall knew about it.
Once in Gibraltar, they lived under cover for two and a half years with the prospect of being moved up to the operation post to be sealed inside. At the end of the war, the team was disbanded and its members resumed civilian life. The Rock was never captured.