Analyst at Bletchley Park

Born: November 11, 1920;

Died: September 24, 2017

CAROLINE Chojecki, who has died aged 96, was a Second World War intelligence analyst who played a key role at the Bletchley Park codebreaking centre, reorganising its database and undertaking research into the possible range of Germany’s newest submarines. Later, she worked at the Soviet Studies Research Centre, which was established at Sandhurst in the 1970s to assess threats from the Soviet bloc.

Originally brought up in Sussex and London, Chojecki, born Caroline Elizabeth Rowett, moved with her family to Helensburgh after the death of her father John. He had committed suicide in 1924 after losing money on a business venture in America and spending £70,000 sponsoring the last Antarctic expedition of his school friend Sir Ernest Shackleton.

The family were shattered by Rowett’s suicide and left in a parlous financial state that required the sale of their homes in England and their move to Helensburgh where Chojecki’s mother Helen could be near her parents. Caroline was sent to St Bride’s School for Girls, where her fees were paid by her uncle. Later she went to Cambridge, where she read modern languages.

On graduating in 1942, she was drafted to serve in the Auxiliary Territorial Service, but was recruited to Bletchley Park by the head of the naval section. She commuted regularly to Cambridge, where she met her husband, Zygmunt Chojecki, a Polish exile. The couple married in 1953 and had three children, who survive them.

At Bletchley Chojecki was superbly organised and made an important contribution to the methodology at the site when in 1943 she introduced a card-indexing system. She had realised that key details of the material intercepted from German signals could easily be lost, while the careful accumulation of information on any individual or craft could quickly develop into a useful profile.

The database grew steadily in size and importance as an analytical tool with Chojecki writing firm information in fountain pen, leaving more speculative details in pencil.

One of her memories of Bletchley was of a cold January afternoon in 1945 when she was struggling up a spiral staircase on her way to see colleagues in the “surface vessels” department.

Chojecki had been doing research into the possible range of German submarines and was carrying a volume of Jane’s Fighting Ships and a copy of Cassell’s World Atlas. As she neared the top of the stairs she collapsed.

Chojecki, who was 24, had pushed herself beyond her limits, having worked flat-out in a continuous state of urgency at Bletchley Park. She was sent to the on-site doctor, who diagnosed exhaustion and prescribed two months’ leave.

His patient was infuriated. As she put it many years later: “It [the diagnosis] was thoroughly unwelcome and I have never been so frustrated in my life. When I got back things were very nearly over, bar the shouting.”

Chojecki’s career took off again in the 1970s when she became a key member of the the Soviet Studies Research Centre (SSRC), which was set up at Sandhurst in 1973. She joined to help with clerical tasks, but her experience at Bletchley Park quickly became evident. She introduced a computerised version of the Bletchley card index system, which became central to the unit’s operation.

She was appointed MBE in 1986 and retired from the SSRC in 1992. In later years she continued living at the family home in Oxfordshire, kept in regular touch with her former colleagues at Sandhurst and kept her eye on eastern European politics.