These worker ants came, mostly, from middle-class backgrounds. Colchester, now 91, had heard of Bletchley through her father, Air Vice-Marshal Sir Charles Medhurst, an air attaché in Rome. At the time, she was living in Italy, where her family moved in high circles – before the war, she had met Hitler and flirted with Mussolini at an embassy party – but she found the prospect of working for her country equally thrilling. “When you’re 19, everything’s romantic and exciting. You’re away from home, meeting all sorts of wonderful people.”
One such person was Pamela Rose, an actress from London, then 24, who had been urged by an interfering godmother to apply for The Park. “I’d just been offered a part as an understudy in a play called Water on the Rhine in the West End, and I was rather excited by it,” she says. “So I asked the man who’d interviewed me what I should do. And he said, ‘Well, the stage can wait. The war can’t’.” Rose, now 97, believes she was recruited on the basis of her well-to-do background: “They seemed to think that if they took in girls from families they knew something about, they were less likely to get a German spy.”
Their work was varied. While Colchester focused on decoding, Rose was stationed in the indexing hut of the naval intelligence section. “The codes came broken up into something like a text message,” she explains. “We had to have a card for the battleship, another for the port it was leaving, another for where it was arriving, and so on. Some days it was incredibly exciting – other times it was very dull, about the captain’s socks or something.”
Others among Dunlop’s 15 Bletchley girls had different roles – Muriel Dindol, at 14 the youngest of the group, was a messenger girl; while Cora Jarman, now 88, professes she still doesn’t know what exactly she was doing. “It was just noughts and crosses on a sheet,” she says. There were, of course, a few female codebreakers – notably Joan Clarke, who worked alongside Turing (played by Keira Knightley in the recent film) – “but they were hardly representative,” says Dunlop.
With its unique mix of military and civilians living in the same quarters (many of them were billeted in nearby villages and bused in and out of The Park each day), Bletchley was an extraordinary experience, with highs and lows. The girls worked shifts through the night in smoky, claustrophobic quarters, and they amused themselves with card games and gossip. “We all used to meet over coffee breaks in a little room in the main house,” says Colchester, who can still sing the ditties she learnt by heart seven decades ago. “There was a pressure to work, but it was very much a together community.”
The girls were younger than the men, but they did socialise together – to the extent that it was acceptable at the time. “They might have flirted, but it was all very dignified,” says Dunlop. “They’d never have rolled into bed together.” Indeed, Rose (née Gibson) met her husband, Wing Commander Jim Rose, at The Park – he was head of the air section – and, through him, was introduced to Turing. “I didn’t know Turing well,” she insists. “He was polite and intelligent, but he preferred the company of men.”
The four years at Bletchley flew by – and most of its women subsequently gave up their careers, got married and never looked back. Rose stayed until the end of 1945 and married Jim the following January. Colchester took a more unconventional path, moving from the world of codebreaking to a career in espionage with MI6, where she later crossed paths with Kim Philby, the Cambridge spy.
For the majority, however, Bletchley was the pinnacle of their intellectual careers. “It simply couldn’t have functioned without them,” says Dunlop. “And this goes for all the women of the war – Wrens, land girls, radio operators. Their job was to be the facilitators; but it’s about time we made them the focus.”
Modesty characterises the Bletchleyettes today – every one of Dunlop’s 15 retains the dignity and discretion that made them perfect employees 70 years ago. “There was a sense that we were doing something important,” says Colchester. “I am proud of what we did. But did we feel appreciated? Well, you didn’t think much about that in those days. There was a war on.”
She gained something else from her days at The Park – a lifelong friend. Having been introduced by one of their tutors on the lawn outside the huts, Rose and Colchester struck up a friendship that endures to this day. “That is one lovely legacy of that time,” muses Rose, her eyes twinkling. “As for the rest of it… There are so many people who say they ‘saved the war’. I know I didn’t. But I daresay we did all right.”
* ‘The Bletchley Girls’, by Tessa Dunlop (Hodder & Stoughton, £20), is available from Telegraph Books at £17 + £1.95 p&p. Call 0844 871 1515 or visit books.telegraph.co.uk. Tessa Dunlop will be in conversation with Bletchley veterans at Waterstones Piccadilly on Jan 8 at 7pm. To reserve your place at this free event, email firstname.lastname@example.org