So who drew the map ?
Work on the tunnel started in July 1942 by the OT (Organisation Todt) firm of “Riechert” and later in 1943 by OT firm “Hellenbart” under the command of the Naval Harbour Construction HQ, who were based at number 4 Commercial buildings. The Todt Organisation was a Third Reich civil and military engineering group named after its founder, Fritz Todt, an engineer and senior Nazi figure. The organisation was responsible for a huge range of engineering projects both in pre-World War II Germany, in Germany itself and occupied territories from Jersey to the Soviet Union during the war. It was notorious for using forced labour.
We can see in the map (last post) that a cafe is clearly marked and we doubt any forced or slave labour could have draw such a big map. So we believe it to be one of the OT guards or German contractors. Potentially it could have been post war by a German POW, kept to clean up, describing his home town. Any other information on the map or theories welcome (email@example.com).