By Victoria Bartlett
BBC Hampshire & Isle of Wight
Jerry believes they had a 90% rate of success when code-cracking
Jerry Roberts, 88, was a senior code breaker and German linguist at Bletchley Park - the World War II National Codes and Cipher Centre.
He now lives in Hampshire and believes Britain would have lost the war without what was achieved at Bletchley.
As soon as war broke out in 1939, their code breakers began the important work.
To mark the anniversary, 70 enigma machines are being flown from all over the world to be reunited with the men and women who cracked their codes.
Due to the secret nature of the work many records about what they did were destroyed. Those like Jerry Roberts, from Liphook, are sharing their memories to help piece together an important piece of history.
Route into cryptography
Mr Roberts has described how he came to arrive at Bletchley: "I took my degree in French and German in 1941 and my professor put my name forward to Bletchley.
"I had a letter from the War Office inviting me - and you did not turn down those invitations.
"Shortly after my interview there I got sent a rail pass to go to Bedford to start at the school of cryptography.
"I was very excited about what was to come."
Mr Roberts went on to work in The Testery, which was a medium-sized country house in the grounds of Bletchley.
He was one of eight staff when he started there in July 1942. This number grew to 118 and they were distributed into shifts so that they were breaking codes 24 hours a day.
On 4 September 1939 the sharpest minds in Britain arrived at Bletchley
The German military used the Enigma cipher machine to scramble messages during World War II to keep their communications secret.
An electro-mechanical machine called The Bombe was used to decipher these messages - developed by mathematicians Alan Turing and Gordon Welchman.
The German machine called The Lorenz was an even more complex cipher machine than Enigma. It was used exclusively for the most urgent messages - and these were the ones Mr Roberts had to figure out.
"Enigma was very important because it was used by the German army, navy and air force," he said.
"But you can't compare it with The Lorenz - it is like comparing coal dust and gold dust.
"Our cipher system - which we called Tunny - was a very special beast.
"Hitler had ordered it especially for messages going from army headquarters in Berlin to top generals.
"Our task was to de-code around 50 different consecutive pieces of cipher text and get the clear text from them.
"As soon as we had done that the next steps had to be taken immediately so the whole day's traffic could be deciphered.
"The Germans used certain wheel patterns for one day only and then they would change them so we had to get through as much as possible in a day."
Importance of the job
Mr Roberts enjoyed his work because he felt he was doing something worthwhile. Just seeing who the messages were from made him realise how critical his role was.
"Quite a number of messages were signed by Hitler himself so the content of the messages were very high-level stuff," he said.
He added: "After the war Eisenhower said 'Bletchley decrypts shortened the war by at least two years' and I agree with him.
"People were dying at the rate of 10 million a year so imagine how many lives were saved by this work - you can do the maths."
"The German U-boats were sinking our ships left, right and centre - our convoys couldn't avoid them because we didn't know where they were positioned.
"But once Enigma was broken we could find out this information. Then the sinkings went down dramatically - by 75% or 80%."
Twenty four women worked in the Testery - none of them spoke German
Of the 10,000 people who worked at Bletchley Park during World War II, around 2,000 are still alive, and most of whom have never told their stories. It is only in the last seven years that Mr Roberts has started talking about his experiences:
"My parents both died without knowing what I did during the war. And as recently as the 1990s I was unable to tell my wife exactly what I'd been working on.
He added: "The secret was kept massively well and somehow this was never a problem - my family never probed me."
Tunny was only declassified in 2000, due to its importance - unlike Enigma, which was declassified in the 1970s. Mr Roberts said:
"I wasn't aware of the declassification until 2002 - until then I kept my mouth shut, we all had to."
Remembering the code breakers
He was pleased that former Bletchley Park staff are being asked for their memories and stories of the wartime years they spent there. He has been trying to raise awareness of what these people did during the war.
He said: "For the first time ever I think people are realising what a fine job the cryptographers did.
He added: "The situation with Tunny and Enigma was unique and I don't think it will happen again.
"It was a war where we knew comprehensively what the other side were doing, and that was thanks to Alan Turing, who basically saved the country by breaking Enigma in 1941.
"For the last year I have had quite a one-man campaign to get recognition for him and how he served the country, but also Bill Tutt who broke the Tunny system which was an amazing achievement, and Tommy Flowers who built the first computer.
"People don't make a fuss of them and they should - what's the matter with us?"
To contact Bletchley Park with your memories you can write to Bletchley Park Trust, The Mansion, Bletchley, Milton Keynes, MK3 6EB, e-mail
or telephone 01908 640404.