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LONDON - The Gibraltar chamber had the innocuous name of the "Stay Behind" Cave.

But this was no game. It was a top-secret wartime mission in which six men volunteered to be buried alive in the cave if the Rock were captured by the Germans, so they could monitor enemy movements.

More than 60 years after the end of World War II, a retired doctor from Preston has been named as the chamber's last survivor. Only now has 92-year-old Bruce Cooper broken his silence.

The young British Navy doctor was called to see his Surgeon-Commander and told they were looking for a doctor to do "something special".

The team, comprising two medical officers, an executive officer, and three junior seamen, was warned before it left that it may have to be sealed inside the operation post for as long as a year. The operation was so secret that not even Whitehall knew about it.

Once in Gibraltar, the team 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.