In 1941, Rear Admiral John Henry Godfrey, the Director of British Naval Intelligence, chose Colonel Gambier-Parry as his radio consultant for Operation Tracer, a highly classified, military operation in which a team sealed in a clandestine observation post was to monitor enemy vessels should Gibraltar fall to the Axis Powers.
In January 1942, Gambier-Parry began trials of the radio communications for Operation Tracer, using equipment that he already had at Gibraltar, and sending one of his staff to conduct trials in the excavated radio room.