Her name was Margaret Rock, also known as one of Chief Cryptographer Dilly Knox’s “girls” in Cottage 3 at Bletchley Park, working alongside Mavis Lever.
In August 1940 Knox complained the sexist Civil Service grading system had misclassified Rock as a linguist or clerk rather than a cryptanalyst, which capped her pay regardless of what she actually did. It wasn’t just an advocacy for fair pay, it was also Knox saying the scare quoted “professors” are just fancy titles and grades for men who were not doing any better work than the women.
The top UK salary allowed because of her gender was £195pa. For context, a male senior cryptanalyst at Bletchley on the higher Civil Service grades would have been earning many times more than her in 1940. Rock was doing fourth or fifth best work on the Enigma staff yet capped far below what the men received.
Indeed, it was Rock who broke the Abwehr Enigma (variant G) with Knox and Lever on December 8, 1941. Rock and Lever had cracked the GGG indicator system in October, the precursor stage. Despite the significance of this feeding into the “Double Cross” system and the D-Day deception, and despite being awarded the MBE in 1945, Rock was never graded fairly in her lifetime. She left GCHQ in 1963. The UK Civil Service want you to know this about her:
She remained single throughout her life and lived in her later years with her longtime friend from North Middlesex School, Norah Sheward.

