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Margaret Alice Rock MBE

Junior Administrative Assistant for the Government Code and Cypher School at Bletchley Park
An image of Margaret Rock

Margaret Rock was born in Portsmouth in July 1903 and went to a private boarding school in Enfield (North Middlesex School) and later to Bedford College, London where she developed a talent for mathematics and in April 1940 she was recruited to work as a Junior Administrative Assistant for the Government Code and Cypher School (GC&CS) at Bletchley Park.

Margaret was deployed into the section being run by Alfred Dilwyn ‘Dilly’ Knox working against German Intelligence Services traffic in ‘a row of chunky converted interlinked houses - just across the courtyard from the main house.’ Dilly ran what became known as Intelligence Service Knox (ISK). She impressed Dilly so much by the end of August 1940 that he was to write about her 'Miss Rock is entirely in the wrong grade. She is actually 4th or 5th best of the whole Enigma staff and quite as useful as some of the 'professors'. I recommend that she should be put on the highest possible salary for anyone of her seniority.’ Margaret subsequently was promoted to the grade of 'Linguist’ with a top salary for a woman in the order of £195pa.

Margaret was awarded an MBE in 1945 and after the war went on to work for GCHQ until her retirement in July 1963. She never married and lived in her later years with her long time friend from North Middlesex School, Norah Sheward. Her work is recorded in the official history of the Abwehr Enigma decryption methods used in Knox’s section which was written by her, alongside Mavis and Keith Batey and Peter Twinn. It is entitled ‘GC&CS Secret Service Sigint Vol II: Cryptographic Systems and their Solution.’ The paper (TNA file reference HW43/7) is referred to as Batey, Batey, Rock and Twinn which (as the GCHQ joke ran, sounded like a firm of solicitors in the Home Counties) describes an important facet of the brilliant work carried out by cryptanalysts in Bletchley. Its sensitivity was such that GCHQ only released it in 2011. Her life is also commemorated in Kerry Howard's Dear Codebreaker.

Rock died in August 1983.