Raymond "Jerry" Roberts - one of the last of a top World War II code-breaking team at Britain's Bletchley Park - has died, aged 93, following a short illness.
Captain Roberts, from Liphook in Hampshire, was part of a group that cracked the German High Command's Tunny code at the British listening post. The team is credited with helping to shorten the war by at least two years.
Their decrypts made it possible to read Hitler's own messages during the war, the BBC reports.
Captain Roberts joined Bletchley Park, in Buckinghamshire, as a German linguist and was among four founder members of the Testery section - named after its head Ralph Tester.
Bletchley Park today. Photo: AFP
Their target was to crack a system known as Tunny, which carried the messages of Hitler's top generals and even the Fuhrer himself.
The system used four times as many encryption wheels as the famous Enigma machine - which carried military communications.
Reminiscing to the BBC years after the war when he could finally talk about his work - Captain Roberts said he had taken delight in reading Hitler's messages, sometimes even before the intended recipient.
He described the intelligence the team had gathered as "gold dust" in a 2013 BBC interview.
It was "top level stuff" referring to the movement of entire armies. It proved vital, he said, in the Allied D-Day invasion and helped save many lives.
"We were breaking 90% of the German traffic through '41 to '45", Captain Roberts recalled in one of the BBC interviews.
"We worked for three years on Tunny material and were breaking - at a conservative estimate - just under 64,000 top-line messages." It, he said, had been "an exciting time" whenever the team "started getting a break on a message and seeing it through".
Wanted recognition for colleagues
He received an MBE for his work but campaigned for further recognition of his colleagues - including Enigma codebreaker Alan Turing.
And he argued the Testery group as a whole should he honoured for its work - including Bill Tutte, who broke the Tunny system, and Tommy Flowers, who designed and built the Colossus - which sped up some stages of the breaking of Tunny traffic.
Captain Roberts said the work done at Bletchley Park had been "unique" and was unlikely to happen again.
He said: "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."
The BBC says Captain Roberts worked at Bletchley Park, Buckinghamshire, until the end of the war before spending two years at the War Crimes Investigation Unit, and then moving on to a 50-year career in marketing and research.