Operation Tracer was a World War II Allied military operation designed as a backup plan in case Gibraltar fell into Axis hands.
A room was built as an observation post from which enemy movement could be reported to the United Kingdom. The room included views of both the Bay of Gibraltar and the Mediterranean Sea.
The volunteers included an executive officer, two physicians, and three wireless operators. The original plan was for a one year stay but provisions for up to seven were provided for the men.
In August 1943, once it was evident there would be no need for the Operation, the secret room was blocked off and the provisions were removed.
A documentary about the excavation of the secret room, released in 2012, is called Operation Tracer – Stay Behind Cave
