Among her contributions to the war effort was the breaking of the German diplomatic Floradora code, a task partially accomplished by a team she led.
[2] Her brother, Tony, joined the Royal Air Force, later becoming an ace pilot and the first husband of Deborah Kerr, who was for a while her flatmate in London.
In the summer of 1941 she was told to work on the German Diplomatic Cypher, known to the British as "Floradora", which was believed to be uncrackable.
That spring, the Diplomatic Section moved to new quarters in Berkeley Street in London as part of the reorganisation of Government Code and Cypher School (GC&CS) which replaced Commander Alastair Denniston with Edward Travis; Denniston moved with the Diplomatic section to London and Travis took over at Bletchley Park.
This system had been introduced by the Germans after World War 1, following the successful British decyption of the Zimmermann Telegram.
The British were also in possession of the first fifty lines of the cypher table, which had been captured from the German consulate in Reykjavík before it could be entirely burned.
This, coupled with the laziness of the cypher clerk at the German embassy in Buenos Aires, who always used lines from the page that the British had in their possession, meant that the first (trivial) decrypts were produced in August 1942,[5] 14 months at least after she had started work.
By this time there were 36 people working for her in the German diplomatic section, among them Dorothy Hyson, an American film actress, and Ernst Fetterlein, who had been Tsar Nicholas II's top cryptographer until the 1917 revolution, then defected to the British.
[7] An American intelligence officer, William F. Friedman, wrote in his diary that Bartley had accidentally discovered the reciprocal nature of the German adder book, which was then proven by another member at Bletchley Park, De Grey.