In the early days of Tunny work when all monthly keys were broken on
depths, the recovery of wheels from key was undertaken in Major Tester's section,
either by means of special methods available before the QEP system was introduced,
or by 'old Fashioned Turingery'.
After P5 limitation was introduced on most of the links normally tried
(December, 1943) depths were still occasionally anagrammed on any others that
still used X2 lim. Some monthly keys were broken in this way, but hand methods as
practised in Room 41 were rarely strong enough to break wheels from key of
under 400 letters. Very long key was sometimes broken on Colossus.
No great advances were made until the autumn of 1944 when X2 PSI1
limitation gradually replaced X2 P5 and X2 lim was reintroduced on several
important links. After the start of the daily key change (July, 1943) it was
policy to try as many key days as possible and it became necessary to develop
quick and powerful methods on shorter lengths of key. First the Delta-X5 flag was
invented and introduced, the Modern Turingery (with decibans) and later 6 -
impulse Turingery for X2 limitation.
Therefore, by 1945, the resources and staff employed in the breaking of
chis and psis from depth key had expanded outside Room 41 and included some or all
of the following: -
A skilled key-breaker in Room 41 (and assistant)
The Rectangles Registrar and up to 6 computers.
1 Garbo, 1 handperforator and operators in Room D.
1 Colossus with wheelbreaker and 1 or 2 operators to
(b) Work in Room 41
Work on Turingery in Room 41 involved very little organisation as each job
was undertaken by one man with occasional help from an A.T.S.
Certain members of Room 41 took a particular interest in key-breaking and
specialised in the work. Most of the older members could undertake the job in the
absence of the specialists, and newer members were gradually trained when it
appeared that two key-breakers on each shift might be required.
Unfortunately the specialist key-breakers did not work on a three shift
basis and were by no means always available. However they were always willing to
work double shifts and odd shifts when there were important key-breaking jobs to
(c) Making of Combined Flags.
The flagging of such rectangle was done by one computer, and one computer
was employed in adding the flags together, so that 5 or 6 computers worked at
It proved profitable for the computer adding the flags to record entries