The History of Hut Eight

vertically, so that any 2 messages could be compared together and the number of repeats he recorded by counting the number of holes showing through both Banburies. A scoring system by ‘decibans’ recorded the value of fits and all messages at 26 were compared with 25 positions to the right and left of the level position and the scores recorded.

The completion of a Banburismus can best be explained by a simple example, the type of Banburismus that would take the expert 10 minutes rather than many hours or even days of work. This is our list of fits:

BBC + .2 = BBE hexagram certain
ENF + 3.7 = EPQ pentagram 17:1 on
RWC + .13 = RWL tetragram 4:1 on
PNX + .5 = PIC enneagram certain
QQG + 2.7 = QDU pentagram evens
IUS + 3.3 = IUY hexagram 20:1 on
ZDR + 5.5 = ZIX hexagram 15:1 on
SWI + 4.3 = SUD tetragram 4:1 on
PPD + .16 = PPU tetragram 2:1 against

Note 3.7 = 3 alphabets + 7 letters.

The fits of better than even chance concern the letters of the right hand wheel:

C - E
F - Q
C - L
X - C
S - Y
R - X

One chain X R C L E can be expressed in this form:


We know that those letters must appear in those relative positions in the right hand wheel alphabet. We now 'scritch' the 26 possible positions (R under A, then under B etc.) and cross out those which imply contradictions: the first position, with the reciprocals (R = A, etc) written in and ringed, looks like this:

Here there is the contradiction that L appears under X but X,


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