She was a British origin, lived in France and returned to England once France was attacked by Germans. She joined Womems auxiliary airforce and SOE F section.as agent being fluent in French .
She was sent to France for anti Nazi activities where she was arrested by the Gestapo while meeting a contact in Montélimar in Drôme on 15 September 1943. She was sent north to the Fresnes prison in Paris where she was subjected to brutal interrogation and torture. A few months later in early 1944, she was shipped to Ravensbrück about 50 miles from Berlin. The Nazi concentration camp held approximately 30,000 women and children. With the defeat of the Third Reich imminent, the camp had become a frantic killing centre. Lefort - along with other prisoners - was made to do hard labour for hours such as paving streets by pulling a huge iron roller. By the end of 1944, she was suffering from extreme malnutrition, diarrhoea and exhaustion.
In early 1945, she volunteered to be transferred to a new camp which SS-Obersturmführer Johann Schwarzhuber - the recently arrived deputy commandant of Ravensbrück - said was for sick prisoners. The new camp had been established at Uckermark on the site of a former youth camp for delinquent girls. However Schwarzhuber, who had formerly been responsible for gassings at the women's camp at Auschwitz-Birkenau, had built the camp as an extermination center. Sometime in February 1945 Cicely Lefort died in the gas chamber .