Ralph Paterson Tester (2 June 1902 – May 1998) was an administrator at Bletchley Park, the British codebreaking station during World War II. He founded and supervised a section named the Testery for breaking Tunny (a Fish cipher).
The Lorenz cipher machine had twelve wheels, and was thus most advanced, complex, faster and far more secure than the three-wheeled Enigma. Lorenz was used to encipher top-secret messages between German Army H.Q. in Berlin, and the top generals and field-marshals on all fronts, including Adolf Hitler himself.
Before World War II, Tester was an accountant who had worked extensively in Germany and as a result was very familiar with the German language and culture. He held a senior position in the accountancy division of Unilever.
Recruited to Bletchley Park, and during later 1941 was the head of a small group working on a double Playfair cipher used by German military police. Testery set up in July 1942 under Major Ralph Tester and the three other original founding members, cryptographers and linguists were: Capt. Jerry Roberts, Peter Ericsson and Maj. Denis Oswald, all four were fluent in German. The Testery used hand methods, working on a German hand cipher to break messages enciphered on TUNNY Fish (cryptography) traffic. Messages broken by hand reached 1.5 million places within one year of its foundation. By the war’s end in May 1945, the Testery had grown to nine cryptographers, out of a total staff of 118 organised in three shifts.
A former Testery senior codebreaker and shift leader Jerry Roberts, recalls that, "The imperturbable, pipe-smoking Tester spoke fluent German, but did not pretend to be a codebreaker. The atmosphere in his unit was always positive and friendly, and the personnel were well selected—Tester seemed to find the right niche for everybody. Thanks to Tester's influence the work of the Testery was very well organised."
After the war, Tester returned to Unilever.
- Good, Jack; Michie, Donald; Timms, Geoffrey (1945), General Report on Tunny: With Emphasis on Statistical Methods, UK Public Record Office HW 25/4 and HW 25/5, retrieved 15 September 2010 That version is a facsimile copy, but there is a transcript of much of this document in '.pdf' format at: Sale, Tony (2001), Part of the "General Report on Tunny", the Newmanry History, formatted by Tony Sale (PDF), retrieved 20 September 2010, and a web transcript of Part 1 at: Ellsbury, Graham, General Report on Tunny With Emphasis on Statistical Methods, retrieved 3 November 2010
- Paul Gannon, Colossus: Bletchley Park's Greatest Secret, 2006, p. 168, Atlantic Books, ISBN 1-84354-330-3.
- Jerry Roberts, "Major Tester's Section", p. 250 from pp. 249–259 in B. Jack Copeland, ed., Colossus: The Secrets of Bletchley Park's Codebreaking Computers, Oxford University Press, 2006.
- Michael Smith, Station X, first ed. 1998, revised 2004, p. 152.
- Roberts, "Major Tester's Section", p. 250.
- Smith, Station X, p. 203–204.
- Roberts, "Major Tester's Section", p. 252.