The Tibetan Key

At the end of WWII, captured documents suggested that the occupying Germans might have discovered an extensive labyrinth of tunnels and other workings beneath the English Channel. According to the documents the labyrinth stretched all the way from the French coast to Dover and Folkestone, but a full exploration was apparently interrupted by the invasion of Normandy. No record of the location of the entrance to the labyrinth survived.

In the summer of 1953, two agents posing as tourists took over four rooms on the top floor of the Hotel Metropole in Folkestone. The plan was to search for the labyrinth with ground-penetrating radar using the Hülsenbeck pulse system. Their work was to be carried out in utmost secrecy, with the GPR equipment installed in the basement of the hotel.