Bored in England, Chaudoir spent much of her time gambling, losing, and complaining that because she was Peruvian, she could not find interesting work. An RAF officer overheard her complaints and her name was passed around until it reached Lieutenant Colonel
Claude Edward Marjoribanks Dansey, the assistant chief of MI6, who made contact with Chaudoir using the pseudonym "Mr. Masefield". After mentioning his awareness of her financial difficulties, Dansey convinced Chaudoir to work for
MI6, pointing out that as her father was currently the Peruvian
chargé d'affaires to the
Vichy government and she had a Peruvian passport, she could travel to France under the pretext of visiting him. Bleil gave Chaudoir the code name of "Dorette" and arranged for her to receive £100 a month disguised as alimony payments. Bleil provided Chaudoir with a bottle of invisible ink which she was to use in letters to Chauvel who would pass them on to Bleil. Chaudoir returned to England and reported to MI6, who debriefed her and handed her to
MI5 to be put to use as a double agent. MI5's investigation into her background registered concern about her "lesbian tendencies" and they were unable to confirm Bleil's relationship with the German government. Chaudoir left instructions that "if anything is to happen to me, tell Monica Sheriffe" although MI5 didn't think Sherrife was aware of Chaudoir's espionage work. The MI5 investigation concluded, "She is merely a member of the international smart gambling set." Despite objections by
John Cecil Masterman, Chaudoir was added to the
Double-Cross System team on 28 October 1942 with a new code name, "Bronx", after the
cocktail. She was given a cover job at the
BBC. MI5
tapped Chaudoir's phone, both to monitor her for pro-German sentiments and to keep an eye on her financial situation. Under direction of her Double Cross handler, Chaudoir planted half-truths, propaganda, and invented quotes from real people in her letters to Chauvel. One of her letters claimed that the British had made excellent preparations to defend against gas warfare as well as stockpiling large amounts of chemical weapons for retaliation, which Masterman believed helped dissuade the Germans from using poison gas against England. German communications to Chaudoir indicated that they trusted her reliability as their agent, and her handler in MI5 described Chaudoir as "probably one of our most reliable agents." As the Germans became more anxious for immediate information about any invasion plans, Bleil instructed Chaudoir to send a message to a Lisbon bank indicating when and where the attack would occur. The message could not make use of the invisible ink, so locations were mapped to specific amounts of money. Chaudoir was to send a telegram requesting a specific amount from the bank, which would indicate the location of the invasion, and use one of several planned phrases to indicate the timing. In support of
Operation Overlord, Chaudoir was instructed to send a telegram on 27 May 1944: "''Envoyez vite cinquante livres. J'ai besoin pour mon dentiste''" (English: "Send fifty pounds quickly. I need it for my dentist."). The bank director immediately passed it on to German intelligence. In Berlin, the message was decoded to mean "I have definite news that a landing is to be made in the Bay of Biscay in one week." An entire tank division was waiting at the Bay of Biscay when the Allies landed at Normandy. When the
D-Day invasion took place, Chaudoir sent mail to Bleil explaining why her warning had been incorrect, blaming it on her informant. After the initial landing at Normandy, Chaudoir and other Double Cross agents passed information to their German contacts that Normandy was just a diversion. Chaudoir's letter said, "Only part of Allied force in Normandy operations, bulk remains here at present" and hinted at a second invasion. Toward the end of the war, Chaudoir travelled to Madrid to meet with German intelligence, but was unable to locate a single German spy. After she wrote them a scathing letter, they asked her to use the telegram to the bank method again to let them know if an invasion was planned for Scandinavia or northern Germany. ==Later life==