Testery

The Testery was a section at Bletchley Park, the British codebreaking station during World War II. It was set up in July 1942 under Major Ralph Tester. Four founder members were Tester himself and three senior cryptographers were Captain Jerry Roberts, Captain Peter Ericsson and Major Denis Oswald. All four were fluent in German. From 1 July 1942 on, this team switched and was tasked with breaking the German High Command’s most top-level code Tunny after Bill Tutte successfully broke Tunny system in Spring 1942.

The Testery used hand decrypting methods to break Tunny traffic. Within one year of its foundation, the Testery had deciphered 1.5 million texts by these methods. By the war's end in Europe in May 1945, the Testery had grown to nine cryptographers, a team of 24 ATS, a total staff of 118, organised in three shifts working round the clock.

The logical structure of the Tunny system was worked out by mathematician Bill Tutte (William Thomas Tutte) in the Spring of 1942. Tunny had 12 wheels, and was more advanced, complex, faster and far more secure than the well-known 3-4 wheeled Enigma machine. The Germans were convinced that the Tunny cipher system was unbreakable. Tunny was the cipher system which carried only the highest grade of intelligence: messages from the German Army Headquarters in Berlin and the top generals and field marshals on all fronts. Some were signed by Hitler himself. Tens of thousands of Tunny messages were intercepted by the British and broken at Bletchley Park by Captain Roberts and his fellow codebreakers in the Testery. These messages contained much vital insight into top-level German thinking and planning.

After the Testery had been breaking Tunny for a year by hand, the Newmanry became active from July 1943 under Max Newman. Mathematicians in the Newmanry used machine methods to speed up breaking Tunny. Early on, a machine called Heath Robinson was produced, to help speed up one stage — breaking of the chi wheels, but the Robinson was slow and not reliable. Fortunately, in February 1944 a new machine called "Colossus" became operational; it was the world's first electronic computer. Colossus was designed and built in only ten months by Tommy Flowers of the G.P.O. (Post Office). This had far greater capacity and speed than the Robinson and so the whole breaking process became much faster. The Colossus was essential for making the very fast counts needed to work out the "de-chis", but the psi-wheels and motor-wheels were still broken by hand in the Testery.

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