Captain Raymond "Jerry" Roberts, who has died aged 93, was one of the last surviving wartime codebreakers at Bletchley Park who have been credited with shortening the Second World War and saving millions of lives.
He was the last survivor of the nine cryptanalysts who worked on cracking the German Tunny system which was used by Hitler, Mussolini and high ranking generals - making it possible for the codebreakers to read Hitler's messages sometimes even before the Fuhrer himself.
Captain Roberts was born in Wembley, London, where his father was a chemist. He was educated at Latymer Upper School in Hammersmith and University College where he studied German and French.
It was his skills in German that made him useful to Bletchley. His university tutor, who had done similar work during the First World War, recommended him and, after an interview, he was accepted.
He joined Bletchley as a cryptographer and linguist in 1941 and was one of four founder members of the Testery, an elite unit named after the man leading it, Ralph Tester, which cracked the Tunny code.
The Testery team, which grew to 118 by the end of the war, managed to reverse-engineer the Tunny, which had 12 encryption wheels to the Enigma machine's three - it has been described by Bletchley Park as an incredible feat of dedication.
A spokeswoman for Bletchley said: "Jerry came to Bletchley Park straight from university but they were all in uncharted territory. It was new ground for everybody."
Capt Roberts worked at Bletchley until 1945 before moving to the War Crimes Investigation Unit for two years, where he interviewed witnesses and victims, taking legal statements from them for later use in court.
This was followed by a 50-year career in marketing and research in which he set up his own companies and did market research for some of the biggest brands in the world including Reebok, American Airlines and Holiday Inn hotels.
He was made an MBE in 2013 in recognition of his service to Bletchley Park and codebreaking, and in his later years campaigned for his colleagues to received due recognition for their work.
He was keen to see commendation for the so-called 4Ts - the Testery as a whole, and three colleagues responsible for major discoveries: Alan Turing, who broke the naval Enigma; 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.
Speaking in 2012 after being told of his MBE, Capt Roberts, from Liphook, Hampshire, said: "They did a brilliant job, we were breaking 90% of the German traffic through '41 to '45.
"We worked for three years on Tunny material and were breaking, at a conservative estimate, just under 64,000 top line messages.
"It was an exciting time because once you start getting a break on a message and seeing it through and getting it
"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."
Roberts was part of the Turing's 100th Birthday Party in the Park and delivered the 2012 Annual Turing Lecture in recognition of his former colleague, who committed suicide in 1954 after his arrest for homosexuality, then a criminal offence.
The Bletchley Park spokeswoman said: "In the last six years of his life, Captain Roberts campaigned absolutely tirelessly for awareness and the achievements made at Bletchley Park.
"During the war, people in one room did not know what people were doing in the next room, never mind another department. It's still a jigsaw puzzle even now."
"He was passionate about what he and his colleagues achieved. He did not want to blow his own trumpet but to have the work of his colleagues recognised."
Captain Roberts is survived by his wife Mei, seven children and stepchildren.