Captain Jerry Roberts

Captain Jerry Roberts

Work on Lorenz was initially completed by the Research Section; however in July 1942, this was taken over by the Testery, headed by Major Ralph Tester.

The founding members were Captain Jerry Roberts, Captain Peter Ericsson and Major Dennis Oswald.

hand scribbled notes

Figure 1

Figure 1, provides an idea of staffing and roles in the Testery. Each of the three columns represents a shift: 9am to 4pm (incorrectly labelled 12.00-4.00pm), 4pm to midnight, and midnight to 9am.

The shift leaders, who can be seen at the top of each column, oversaw all of the functions beneath them. The hand scribbled notes (click on the image to view full size) are by Captain Jerry Roberts.

The Testery used hand methods to break Lorenz and consisted of linguists and codebreakers. The Newmanry was founded in mid-1943 under Max Newman to develop machines to speed up the hand work of the Testery and consisted of mathematicians and engineers.


The video below shows a lecture given by Jerry Roberts on the Testery:

The Testery broke Lorenz by hand for a full year with no machine help, including the crucial messages relating to Kursk in 1943. Figure 2. is an example of breaking a depth by hand as written by Captain Jerry Roberts (at 93 years old).

Testery Figure 2

Figure 2 – click on the image to view a transcript of this page

From mid-1943 to the end of 1943 messages were broken with the help of Heath Robinson, which found the chi wheel settings. The psi-wheels and motor-wheels were broken by hand by the cryptographers and support staff in the Testery. Although Heath Robinson sped up the process, it was rather slow and not very reliable.

Heath Robinson

A close up of Heath Robinson

From January 1944 to the war’s end messages were broken with help from the Colossus computers, which replaced Heath Robinson in finding the Chi wheel settings. The psi-wheels and motor-wheels continued to be broken by hand in the Testery to free up the Colossi.

The Testery broke up to 90% of traffic during the Colossus period. Without the Testery breaking messages, there would have been no Lorenz decrypts at all. See Bletchley Park for examples of the significance of breaking Lorenz and Enigma.

Punched Paper Tape on Colossus

Punched Paper Tape on Colossus

The Testery was eventually located in Block F at Bletchley Park.  Construction started in January 1943 and the Testery and Newmanry moved into the Block in September 1943. The below pictures are of Block F in the 1980s taken by J.E Hoad and are reproduced with kind permission of the Bletchley Park Trust (please click on image to view full size).