As crowds filled Britain's streets to celebrate the end of the Second World War, there was one part of the victory story that couldn't yet be told.
The efforts of thousands of codebreakers, working in secrecy in basic huts at Bletchley Park in Buckinghamshire, are thought to have shortened the war by at least two years, saving millions of lives.
Bletchley's most famous figures such as Alan Turing – played by Benedict Cumberbatch in the Oscar-nominated film The Imitation Game – were male, but in reality Bletchley was a woman's world: eighty per cent of the 9,000 staff were female.
Bletchley was the headquarters of the Government Code and Cypher School, where cryptanalysts mined data and unlocked enemy communications – most importantly those encrypted with the Enigma cypher, which were vital to tricking the Germans about the location of the D-Day landings.
Many women were pivotal to the operation, but few were formally recognised as codebreakers working at the same level as their male peers.
Leading male codebreaker Dillwyn "Dilly" Knox was an eccentric classics scholar - an expert in ancient Papyrus. He specifically requested an all-female team to work with, who were nicknamed "Dilly's fillies" or “Dilly’s girls".
Jean Pitt-Lewis, a 90-year-old who became part of Dilly's team as a teenager, believes being an all-women troop was key to their success.
“You don’t get the same sort of distractions if you don’t have men, I think," she tells me at the launch of 'The Debs Of Bletchley Park', a book by Michael Smith about the female codebreakers. "I say this because when my husband set up a business, much later in life, he always insisted that he only employed girls, because he said there were too many distractions [with men].”
The fact that men were in charge of the overwhelmingly female staff at Bletchley didn’t bother her. “It was natural in those days that the men were the bosses,” she says, “much more so than today.”
Like the other young women, Pitt Lewis arrived at Bletchley with little knowledge of what she would be doing. At the site - a Victorian mansion surrounded by plainer buildings - she was immediately made to sign the Official Secrets Act, swearing not tell a soul about about what happened at Bletchley for 30 years.
This included family, boyfriends and even the other girls – many didn’t know what women yards away from them were doing.
Secrecy dictated their lives. One girl revealed the truth to an American GI at a dance. He dutifully informed her superiors of her indiscretion, and the other women never saw her again.
Many were reassigned from the military or civil service, had secretarial training, or came straight from school – few went to university in those days.
Pitt-Lewis had an interview with Knox to become one of his "girls" at just 17. "It was a bit of a farce", she recalls. She had just finished school but had been rejected the Women's Royal Naval Service, the Wrens, because she was too young.
"I always thought that if I had joined the Wrens, I would have ended up at Bletchley anyway, doing something far less interesting than I was,” she smiles.
"In the interview, Dilly asked me if I knew any German. I said no. That was about it." She was in. Knox did warn her that some of the Bletchley girls were fairly radical. One was “a very nice person, but a bit odd," he cautioned. "She wears trousers and a bow tie, and she smokes a pipe”.
Women were expected to look ‘like women’ in those days, Pitt-Lewis explains: “I had a tremendous argument with my father while I was working at Bletchley. I was planning to go to nearby Aylesbury to buy myself a pair of trousers. He said, 'You’re not going to do anything of the sort.' He was absolutely horrified at the idea.”
The teenage Pitt-Lewis claimed she needed trousers because it got chilly on night shifts at Bletchley (“I didn’t actually do night shifts that often but it was a good story,” she admits mischievously).
“I said ‘It’s my money and I’m going to buy them.’ I was being thoroughly bolshy. He’d be horrified if he thought I wore trousers practically all the time these days. But it was a different age then.”
On shifts as a codebreaker, Pitt-Lewis tried to decode messages as they came in, using Dilly’s system of “rodding”: turning rods marked with letters to try and work out the rules used to scramble the messages.
“We had this little pile of what we called sticks,” Pitt-Lewis says. “They were sort of rods with the alphabet on them. We worked in three colours because there were three wheels that we moved. Everybody just grabbed a pile, either red, blue or green. It was a certain amount of chance as to whether we actually managed to decipher it.
"I think we were pretty good - there weren’t many days when we missed out. Dilly had worked out this amazing system but initially it was very much trial and error."
Work was never discussed when the women were off duty. “We didn’t even chat about it amongst ourselves," says Pitt-Lewis. "We just never thought about it. We’d signed the Official Secrets Act and that was that. It meant a great deal in those days I think, a bit more than it does these days. People seem to not care quite so much about keeping secrets.
"I think the security was absolutely complete, which is amazing when you consider the number of people who were here.”
Bletchley women were billeted among local families, or slept in double bunks in the huts in the park’s grounds.
Bletchley veteran Betty Webb, now 92, recalls the "primeval" conditions. "There should have been about 18 people to a hut, but there were often a great many more. The camp was literally thrown up and it was jolly cold in the winter and jolly hot in the summer."
"The heating was from these awful stoves, half the time we didn't bother to light them because they belched smoke in every direction. They were really quite dangerous. We did have baths but you had to queue and sit on the floor, and we only had four inches of water."
Webb agrees that it became second nature to never speak about their work: “We knew that we just didn’t talk about anything. Sometimes, when I was billeted, my landlady would ask what I had been doing that day, and I’d just say ‘Oh, a rather boring secretarial job, end of story,’ and talk about something else.”
When I meet Webb and Pitt-Lewis, gathered other veterans, each woman proudly wears a gold and blue broach - not a medal - which they were awarded for their work only in 2009.
Webb thinks women’s contribution to the crucial intelligence operation still hasn’t been properly recognised. “I don’t think people realise it at all. It’s difficult to tell why.
"I suppose - in some theatres of life - women are thought to be incapable, which is rubbish. I mean, you can have a woman dentist and a doctor and whatever now. But I think women are still a little bit diffident about coming forward. They are different animals.”
Webb is grateful for the profile of women such as Mavis Batey, a star Bletchley codebreaker who was so adept at reading messages that she worked out that two Germans shared one girlfriend called Rosa.
“She had the guts, if you like, to say I’m going to have a go at this, and she made it. But she was very unusual.”
Their clandestine existence gave the women a sense of camaraderie, she adds, “because we were all here, because there was a war on and we were all fighting to one end.”
Working at Bletchley was a well-paid job: and the staff didn’t need to pay for food, accommodation or uniforms. “We were quite well off,” says Webb.
Some enjoyed choirs, plays and other clubs in their time off, and others made the short trip to London to see boyfriends.
They were also promoted often. Webb says: “I think it was meant to keep our pay in line with the civil servants. I was promoted up to staff sergeant by the time I left, so I was paid accordingly.”
Webb was seconded to Bletchley as a member of the Auxiliary Territorial Service. She was not a codebreaker, but her job was crucial.
She worked to register messages as they were received from the German police forces – some of the first intelligence that revealed the massacres of Jews on the Eastern front, which we now understand as the Holocaust.
But she had no idea that she handled that information until 30 years later, when the Bletchley story could be made public. “I wasn’t aware of it at the time. The only people who would have done would be a handful of very senior people such as Dilly Knox, and Turing of course. To me, the messages would have looked like any others. There would be no indication at that stage as to the content.”
When I ask her what it means to know she helped the Allies discover the historic atrocities, she looks embarrassed: “Well... obviously it’s very gratifying.”
Webb was one of few women who continued working long after the Bletchley Park days. She was unusual.
“Most women just wanted to marry and have children. Nowadays far more women put it off for much longer, and then they try and balance a job with a baby which must be very difficult.”
She went into the army, serving until 1969. “In the main I was a permanent staff officer to the territorial army units, but I finished up being the recruiting officer for the whole of the West Midlands – it was a big job, that was, I had twelve sergeants to help me.”
Why did she feel the pull to keep working? “I don’t know, I didn’t find the right man I suppose.” She did later marry, although her husband sadly died eight years later.
Like many others, Pitt-Lewis stopped working four years after the war, in 1949, to become a mother and wife. “The husband was supposed to support the wife a little bit in those days,” she laughs, “but, my husband set up a small printing business and I did join him in that eventually.”
Didn’t she miss the excitement of the war? “I don’t think so. I mean, I’d had a very fascinating life. After the war I went out to Ceylon [now Sri Lanka] and India, and met my husband out there. I’ve had a very lucky life.”
After 1975, the veil finally lifted and the women were finally allowed to speak about the experience and their contribution to the war.
“My mother rang me in an ecstatic phone call the next day," says Pitt-Lewis. "[Journalist] Ludevic Kennedy was interviewing [F.W.] Winterbottom who wrote the first book about us.
"My mother said she didn’t normally listen to the programme on the television, but she was too lazy to get up and turn it off. 'At last I know what you were doing!' she cried. It must have nearly killed her not knowing I think, because she did like to know what was going on."
Now the secret is out, Webb is one of the most vocal of Bletchley's surviving women, speaking often to events and media. It's important, she thinks.
“I’ve done over 100 talks about Bletchley," she smiles proudly. "Because we need to keep this atmosphere alive, and so I speak to as many people as I can and impress upon them the importance in coming to Bletchley. I’m not sure how many do, but I know that when they do, it’s partially the result of me giving them a little push".