This Monday, the Phoenix cinema is hosting a special screening of The Imitation Game, the new biopic of famous World War II mathematician Alan Turing, who played a key role in cracking the Nazi Enigma code. In keeping with Remembrance events taking place across Britain this month, the night will give audiences a chance to hear from a real life code breaker, North Finchley resident Ruth Bourne.

The 88-year-old worked at Bletchley Park from 1944 to 1946 as part of a remarkable operation involving 1800 women.

Having joined the Women’s Royal Navy Service (popularly known as the Wrens) straight from sixth form, Bourne travelled down from Birmingham to take part in the operation. Immediately, she was bound to secrecy.

“My role was told to me when we got there. There were half a dozen or so of us who were not categorised, so we were told by the Wrens petty officer that we were going to do secret work. There’d be no promotion, the pay was the lowest rating, it was anti-social hours, and so if we didn’t want to do it, now was the time to say and we’d be transferred to another category. We all said yes.

“Then they told us one sentence at a time that we were breaking German Codes. That was all we knew – all I knew certainly – so I didn’t realise that I was part of this chain of code breakers and the machine I was operating, while it didn’t break a code by itself, was speeding up the operation.”

The Bombe machines initially designed by Alan Turing were made to decipher the equivalent of 36 Enigma machines, which the Nazis used to send secret messages, in a quarter of an hour. Working on these, Bourne was responsible for fixing the circuits and changing the drums which mimicked the Enigma rotors.

There were two atmospheres, she says, to be found at Bletchley: the normal, relaxed mood within dormitories where the girls would talk about boys and normal 18-year-old life – “which is probably the equivalent of 13-year-old life now, we were very naïve” – and the pressurised, demanding work shifts that required you to be “125 per cent accurate”.

Relieved to have found a job straight from school however, Bourne didn’t mind the intensity. “I found it interesting and it was within striking distance of the west end of London.

“I had come from Birmingham, and to me London was always a Mecca. Everything from the bright lights… well they weren’t bright lights, but the theatre and the stage door canteens and the cheap opera and free tickets – it sounded glamorous.”

After the atom bomb was dropped on Japan in 1945, the teenager’s job suddenly changed as the workers were forced to dismantle the very machines they had spent months maintaining. The reasons for this are still unclear, but nonetheless the group “sat there with a soldering iron and every wire and every connection was dismantled and sold off as army surplus. And then they didn’t know what to do with us.”

The war by this point was over, but Bourne had studied shorthand typing at school and used her skills to retrain. She met and married an RAF officer, settled in London and, after a brief stint as a Kindergarten teacher, set up the Bendix launderette franchise with her husband. “There I was,” she says, “sitting in front of 12 machines with the drums going round; it was really a home from home, wasn’t it?”

It was certainly a curious irony, but one she had to keep to herself. The secret oath taken by Bletchley workers meant they had to keep silent for 30 years, and both of Bourne’s parents died before she could tell them of her role during the war.

When the story was finally revealed in F. W. Winterbotham’s 1974 book, The Ultra Secret, she finally realised the true scope and significance of the operation she was involved in. Yet when she took the book to her husband and said this was what she had done, his response was distinctly measured. “He said that’s nice dear,” Bourne laughs, “Now what’s for tea?”

Now working at Bletchley Park once more as a tour guide, Bourne is one of many bringing the story of its many wartime women workers to the masses. The Imitation Game will rightly bring the revolutionary work of Alan Turing into public consciousness again, but who would have thought a teenage girl seduced by the West End would play such a crucial part too?

Ruth Bourne talks at the Phoenix Cinema this Monday. Visit phoenixcinema.co.uk