General Report on Tunny

14B page 29

daily wheel change was introduced in the summer of 1944, the combined sections took it in their stride. The main division of work remained unchanged to the end, though an increasing amount of wheel-breaking was done by Major Tester's section as P5 was dropped and depths became more frequent, and an increasing amount of motor and psi setting was done by machine as soon as the number of Colossi made this possible.

(c) Combined operations.

In general Testery methods were hand methods based on language properties, and Newmanry methods were statistical and needed machines. But there were many contradictions. The computing of Rectangles is a statistical hand job undertaken by the Newmanry, and on the other hand Dragon is a machine designed to do a language job in the Testery. Hand analysis of key (by methods elaborated from that devised by TURING in 1942) is a statistical hand job involving probability techniques which was done by the Testery before (and after) the Newmanry was founded.

The decoding room grew up as part Major Tester's section and remained so. A joint Registry was founded in January, 1944.


The following brief notes show the general set up of the operational organisation in its final stage of development. Every department was staffed 24 hours a day.

(a) Control and registration.

The Control Officer maintained all contacts with Knockholt and Hut 3. In particular he was responsible for informing Knockholt which links were to be covered and which messages were required for wheel-breaking or setting.

Z-tapes for all messages required were prepared at Knockholt and teleprinted in the case of wheel-breaking tapes to Block H, and in the case of setting tapes to Room 11, Block F. Red forms were sent by bag.

The joint registry in Room 12 was responsible for arranging the circulation of these tapes and relevant documents to the Newmanry, the Testery cryptographic departments, and to the decoding room. The registry itself kept all material not in direct operational use, and arranged the disposal and storage of materials relevant to decoded and abandoned messages on which further work was unlikely. This arrangement was of great value in keeping the number of tapes and papers in operational room to a minimum. "Room 12" had two branches: the T-Registry in Block H for dealing with wheel-breaking tapes and the Main Registry in Room 12 itself for dealing with setting tapes.

(b) Mr. Newman's section.

Wheel-breaking activities took place in Block H under the direction of the Wheel Man, setting activities in Block F under the direction of the Duty Officer who also had general charge of the section's activities on his shift. Each Block contained a Registry, Tunny Room and Colossus Rooms.

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