An alternative, independent intelligence-gathering network run by the Secret Intelligence Service prior to World War II in parallel to, but in isolation from, the conventional Passport Control Offices. Z personnel usually operated under commercial or journalistic cover across Europe. They were directed from offices in Bush House, on the Strand, and were attached to such businesses as Geoffrey Duveen & Co., Alexander Korda’s London Films, and a travel company. In addition, Z’s chief, Claude Dansey, succeeded in recruiting many of his personal contacts, among them some well-known foreign correspondents such as Geoffrey Cox, Frederick Voight, and Eric Gedye.
In September 1939, Z personnel were instructed to make themselves known to the local passport control officer (PCO), wherever they were, and to continue their intelligence-gathering activities in tandem. In reality many PCOs were skeptical about the quality of Z personnel and the reliability of their networks. When Capt. Sigismund Best was abducted at Venlo in November 1939, it was assumed that whatever advantage had been achieved by the Z Organisation had been compromised permanently.
Siegmund George Warburg has worked under cover for the Z Organisation In the period immediately before the Second World War. He reported from Switzerland on his regular meetings with Hjalmar Schacht, then the president of the Nazi German Reichsbank and thus the most powerful German banker.
See as well: Z Special Unit, Use of Z symbol in Russia/Ukraine War