FOR more than 30 years she kept a discreet silence about the role she played in helping the Allies beat the Nazi war machine.
Ann Mitchell’s closest family and friends were told only that she had been a temporary assistant with the Foreign Office during the Second World War.
But the truth she was forced to hide from them was that she had spent two years cracking German codes at a secret British intelligence base.
Now the Edinburgh grandmother is to relive her Bletchley Park experiences at a screening of the blockbuster film Enigma, which was inspired by the codecrackers’ secret work.
A real Enigma machine will also be unveiled by the National Museums of Scotland to coincide with the screening at its Lumiere Cinema on Saturday.
The machines produced coded messages so complex the Nazis believed they could not be broken.
But the chance capture of an Enigma machine allowed the Bletchley Park team to break the code and intercept Nazi commands, potentially saving thousands of lives. Mrs Mitchell, who lives with her husband Angus in Regent Terrace, will recall her wartime experiences in a talk before the screening of the film, which stars Kate Winslett and Dougray Scott.
Appearing alongside Mrs Mitchell will be one of her former Bletchley Park colleagues, Marigold MacKintosh, who also lives in Edinburgh.
Mrs Mitchell, 79, said: "I had graduated with a degree in mathematics from Oxford University and when I went to see their appointments board they recommended I apply for work at Bletchley as an assistant at the Foreign Office. I had no idea what went on there, even when I took the train there for my first day, but then I was asked to sign the Official Secrets Act. It was very exciting.
"Although we were cracking the codes every day, we never really knew what the intercepted messages meant. We just knew we had to battle against the clock because the Germans changed their messaging system at midnight.
"I worked there for two years, from 1943 to 1945. My last day at work was VE Day in 1945 when we were all told we wouldn’t be needed any more."
Mrs Mitchell - one of an estimated 7000 people to work at Bletchley Park during the war - praised the hugely successful film, which she has seen twice since its UK premiere at this year’s Edinburgh Film Festival.
She said: "I thought the book that the film was adapted from was very well researched and the film was pretty faithful to the book. It changed a few things but at the end of day it’s a work of fiction based on fact.
" It brought back a lot of memories about the atmosphere of working in Bletchley. It’s quite astonishing that there’s now so much interest in something that happened so long ago."
The Enigma machine in the National Museum of Scotland’s collection was previously on display in 1995 as part of an event celebrating the 50th anniversary of the end of the Second World War.
The museum bought it at auction in the mid-1990s, and it will now be on display until the start of February.
Alison Morrison-Lowe, curator of the history and science section at the Royal Museum, said the machine was being put on display in the cafeteria outside the entrance to its cinema.
"It seemed an appropriate place to put it so everyone going into the film can have a look at it. We think people will be absolutely fascinated.
"The Enigma machine we have was one of several to be smuggled out of Germany but we think it is one of just four in the UK, including one which is on display at Bletchley Park itself."
Richard Mowe, director of the Lumiere Cinema, said: "Enigma is a film that really seems to have captured the public’s imagination.
"It just seemed a perfect match to be able to show the films, put a real Enigma machine on display and have a couple of real Bletchley girls come along to talk about working there."
Enigma is screened at the Lumiere Cinema on December 7, 8, 14 and 16. Mrs Mitchell and Marigold MacKintosh will be speaking before the December 8 screening.