It took Sidney Goldberg more than 30 years to tell his wife, family and friends what he did during the war.

It was only in 1974, when Frederick Winterbotham wrote The Ultra Secret, the first account of decryption operations during the war, that Mr Goldberg and the other 25,000 code-breakers began to reveal their experiences.

Mr Goldberg, now 86 and living in Kenton, north London, is one of 35 veterans to attend a special ceremony at Bletchley Park today to receive a new award for services to the Government Codes and Cipher School (GC&CS).

Born in Leipzig in 1923, Mr Goldberg moved to the UK at the age of 11. At the age of 18, two years into the war, he put his language skills to use and became a signals interpreter, intercepting German aircraft messages, in the RAF.

“They were very short of staff and so took on Jewish people because we knew Yiddish — even though that wasn’t much help with German,” he said. There was no introduction or training. “I was put in front of a radio and told to twiddle.”

Even 30 years on, when their obligation under the Official Secrets Act was lifted, Mr Goldberg still kept quiet. “I’d just got used to it by then and it didn’t feel strange,” he said.

Morris Hoffman, now 93 and living in New Barnet, became involved after a professor at Birkbeck College, where he was studying languages, suggested he apply for a position advertised by the Foreign Office for German speakers.

On February 12 1942, he arrived at Bletchley Park. “The deciphering was being done in Hut 6, next door to our hut, and the deciphered messages were passed to us through a hole in the wall, to be emended, translated, evaluated, and sent to the Defence Ministry.”

With the help of decryption machine, Enigma, Mr Hoffman made crucial maps of German troop locations.

At the age of 18, Gordon Rosenberg found the idea of signing up to a secret unit a thrilling concept. His ambition to fly for the RAF was snatched away after he was found to be colour-blind.

He had an interview for the codes and cipher unit and before he knew it, he had been vetted, signed the Secrets Act, and was sent to Bletchley Park.

Mr Rosenberg, now 87 and living in Westcliff-on-Sea, said: “I didn’t know the importance of it at the time.”

Today is the first time he has returned to Bletchley Park in more than 60 years. Like his fellow Jewish veterans, he remains incredibly modest and humble about his work, which, historians argue, reduced the war by two years.

“I never looked for recognition so I was surprised to get the award. I think I was privileged to do the work I did, particularly as I was Jewish. There was a lot of prejudice around then but no-one I worked with ever said anything — we all just got on with the job.”