Margaretha Geertruida "M'greet" Zelle McLeod (7 August 1876 – 15 October 1917), better known by the stage name Mata Hari, was a Dutch exotic dancer, courtesan, and accused spy who was executed by firing squad in France under charges of espionage forGermany during World War I.
During World War I, the Netherlands remained neutral. As a Dutch subject, Margaretha Zelle was thus able to cross national borders freely. To avoid the battlefields, she travelled between France and the Netherlands via Spain and Britain, and her movements inevitably attracted attention. In 1916, she was travelling by steamer from Spain when her ship called at the English port of Falmouth. There she was arrested and brought to London where she was interrogated at length by Sir Basil Thomson, Assistant Commissioner at New Scotland Yard in charge of counter-espionage. He gave an account of this in his 1922 book Queer People, saying that she eventually admitted to working for French Intelligence. Initially detained in Cannon Street police station, she was then released and stayed at the Savoy Hotel. A full transcript of the interview is in Britain's National Archives and was broadcast with Mata Hari played by Eleanor Bron on the independent station London Broadcasting in 1980.
It is unclear if she lied on this occasion, believing the story made her sound more intriguing, or if French authorities were using her in such a way, but would not acknowledge her due to the embarrassment and international backlash it could cause.
In January 1917, the German military attaché in Madrid transmitted radio messages to Berlin describing the helpful activities of a German spy, code-named H-21. French intelligence agents intercepted the messages and, from the information it contained, identified H-21 as Mata Hari. The messages were in a code that some claimed that German intelligence knew had already been broken by the French (in fact it had been broken not by the French, but by the British "Room 40" team), leaving some to claim that the messages were contrived. However, this same code, which the Germans were convinced was unbreakable was used to transmit the Zimmerman Telegram; its unintended interception some weeks later precipitated the United States' entry into the war against Germany.