Joanna Chorley

Joanna Chorley, circled, and her fellow codebreakers at Bletchley Park in the photograph taken in 1945 (Photo: Geoff Robinson)

This piece first appeared on the Technicians Make it Happen website (11/4/2019). Below is the full version.

In 2014, Joanna Chorley (1925-2019) found a photograph of herself and thirty-nine operators who worked at the code-cracking centre, Bletchley Park. The photograph, the existence of which broke secrecy laws, was kept hidden for decades in a desk drawer, until she discovered it shortly before the 70th anniversary of Colossus. It was a photograph that shot Joanna Chorley to national attention and shone a light on the work she and the other women had been doing 70 years previously at Bletchley Park, the place Churchill described as “the goose that laid the golden egg but never cracked.”

Joanna Chorley, circled, and her fellow codebreakers at Bletchley Park in the photograph taken in 1945 (Photo: Geoff Robinson)
Joanna Chorley, circled, and her fellow codebreakers at Bletchley Park in the photograph taken in 1945 (Photo: Geoff Robinson)

Joanna, née Stradling, was just 18 months old when her mother died. They had travelled to Egypt to see Joanna’s father, Squadron Leader Dick Stradling, where he was based. While in Cairo, Joanna’s mother contracted typhoid fever and dysentery and ultimately succumbed to them. Her death left a distraught husband and a baby with whooping cough who had to be repatriated back to England to live with her grandmother in Cirencester.

As with many fathers of that time, Dick Stradling was a distant figure in his daughter’s life. He remained in the Middle East until 1930, returning only once in that time to see her. Joanna said of that visit, “He put his head around my bedroom door and said “Cuckoo!” and I just screamed the house down.”

After boarding school, Joanna was barred from attending university by her father so attended domestic science college instead. However, she cut short her time there, joining the Women’s Royal Naval Service, or Wrens, aged 19. She joined hoping to be sent to sea but that was not to be; instead, she was given the choice between map plotting and working on light electrical instruments in the country. Little did she realise that the choice she made would bind her forever to a national secret. She chose light electrical instruments because, as she said, “I always liked nut and bolts.” So in 1944, she ended up at Bletchley Park in Buckinghamshire, the British centre for cracking German and Italian military codes.

It must have been quite an introduction to Bletchley Park for a 19-year-old: a series of ominous lectures, warnings about loose lips, and the signing of the Official Secrets Act. However, she was not alone; she arrived with 20 other girls and there were around nine thousand military and civilian personnel working at Bletchley, three quarters of whom were women. So many people, in fact, that accommodation in rural Buckinghamshire became a real issue.

Many Wrens slept in draughty and cramped barracks with 70 others. The lucky ones lived in old manor houses which had been commandeered to house the large new workforce. Joanna was sent to Woburn Abbey, a former home to Cistercian monks, which was by then a Palladian mansion. It might have had beautiful views, mahogany baths, brass taps, and general splendour, but even that couldn’t quite make up for the eight-in-a-room bunk beds. Joanna recalled, “It really was jolly cold.” She said, “The bath had a black line on it at 5 inches, even though there was masses of water. We just accepted the rule, because if we went over the line then boring things might happen.” It was at Woburn Abbey that the photograph of the 40 Wrens in their naval berets was taken in 1945.

There were some advantages to being based at Woburn Abbey. She said, “In our spare time, we all had bicycles and we used to bicycle all over the place. We used to bicycle about three miles to where a doctor kindly lent us his tennis court and we’d play tennis.” Alongside the tennis and bicycles there was swimming. “We used to swim in a reservoir,” she remembered, “Full of ice-cold water but we didn’t mind!” It also gave the opportunity to explore the grounds where, bizarrely, Père David deer, bison and wallabies roamed. These exotic animals had been collected by the Abbey’s then owner, the eccentric (and Nazi-sympathising) Duke of Bedford. It offered fresh air away from the pressure and strict routine of Bletchley.

Bletchley Park was a factory for breaking German and Italian codes. All the workers’ roles were in some way oriented towards that goal. There were huts full of human calculators, cryptographers, and machines that worked 24/7 on different encoded messages that would arrive from listening stations around the country. By the time Joanna had arrived in 1944, Bletchley was routinely cracking the Enigma code which was used by the German army. More of a challenge were the so-called Fish messages sent between Hitler and his senior high command which had been encoded using a Lorenz encoder. The Fish messages were made up of a long string of dots and crosses that required machines to crack efficiently.

Chorley’s first job was mending and transporting the paper tape on which the messages were punched out for the Robinson machines. These machines, named after the cartoonist Heath Robinson, were designed to help crack these Fish codes. The Robinson machines worked through the many possible settings on the Lorenz encoder, looking for one that fitted the message to give a first clue in how to crack the code. Joanna later worked feeding the coded paper tape into these machines where it would be compared to another piece of tape pre-punched with the various Lorenz settings. It was difficult and hot work keeping two tapes exactly in synch while running them through the machines at 2000 characters per second. Ripped paper and papercuts were a constant hazard.

Chorley was strongly motivated to keep at her work because of a glimpse of the future. “I met Colossus just after I had signed the Official Secrets Act,” she said. “I saw this astonishing machine the size of a room. It was ticking away, and the tapes were going around and all the valve, and I thought, what an amazing machine. There were valves and transistors and flippy-flappy things. Like magic and science combined.” The Colossus, which Chorley had fallen in love with, was the world’s first electronic programmable computer and would replace the unreliable Robinson machines. It was the size of a sitting room but, despite requiring over a thousand valves, was more efficient and easier to run than the Robinson, requiring only one tape. It could read 5000 characters per second – faster than anything ever produced commercially ever since – with the paper tape travelling up to 30 miles per hour.

Colossus codebreaking computer in operation (1943) Source: The National Archives (FO850/234)
Colossus codebreaking computer in operation (1943) Source: The National Archives (FO850/234)

There was a minimum height required to work on the Colossus, such was the size of the machines. Chorley wasn’t that tall but she had long arms and so she got her dream job. Working with a cryptographer, Chorley and another Wren would be operating the complex array of switches and dials and feeding paper into Colossus. They would check the printed output to see if they had found a match between the settings and the code. Chorley said of this work, “We obviously knew that we were involved in breaking code of some sort or cyphers. What they were we did not know. We never knew the result, at least our little lot never knew the result […] all we did was set the wheels.” These machines could never be turned off, so Wrens worked in shifts throughout the night.

If the Colossus found a match the settings and message would be sent through to another hut where it would be decoded into German to see if it made sense or came out gibberish. If the decoded message was gibberish, then it was sent back and another attempt was made at finding the wheel positions. Towards the end of the war Bletchley Park was working so smoothly that they were cracking codes and sending them to the allied forces before the German generals, for whom the messages had been intended, had received them. The workers did not discuss the work even with each other and while this intense secrecy brought an element of excitement for some workers much of the work was very boring. For Chorley, “It was exciting because of the machine, but not everyone found it so; some people thought it was boring.”

Two days before victory in Europe was declared, Chorley and her colleagues sensed the war had ended because of the increasing number of the messages and rumours coming from the other huts. They celebrated the leaked new of Germany’s fall, still officially top secret, by decorating a tree with toilet paper but were severely criticized when spotted by senior staff for doing so – as Chorley recalled, “They tore a strip off us”.

After Bletchley, Chorley applied for a position as Educational Vocation Trainer in the Navy, training men and women returning from the war for life on civvy street. She taught them how to cook, use a ration book, and get back to work, even though she had never done any of these things herself! It was during this time that she met her husband-to-be named, like her father, Dick, and within 18 months of meeting they were married.

Chorley never returned to a technical role but in her later years the mother-of-three worked as a domestic bursar for a number of schools. However, her favourite job was furnishing properties for The Landmark Trust, which she continued to do until she retired. “It is the job I am proudest of,” she said.

Joanna Chorley is now 88 (Geoff Robinson)
Joanna Chorley is now 88 (Geoff Robinson)

All those who worked at Bletchley Park took secrecy seriously and many, like Chorley, kept silent until 1979 when the story of Bletchley Park was made public. “If you’ve kept something secret for 30 years, you’ve forgotten about it mostly,” she said. “And even now, today, some bits of what I’ve done I think, ‘I don’t think I’ll say anything about that’.” Joanna eventually retired to Stony Stratford, a few miles from where she spent those important years at Bletchley Park. In 2017 she was presented with the ‘Bletchley Park commemorative badge’, issued by the Government Communications Headquarters (GCHQ), at Bletchley Park.


Most of this article came from this very interesting book by Tessa Dunlop called the The Bletchley Girls (2015, Hodder & Stoughton). The images of Joanna come from a 2014 Telegraph article. There is also a BBC recording of her voice.

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