This was the simplest form of dummy depth and, as will be realized, the solution of it was extremely easy and could in fact be found by consultation of a chart listing all known dummy expressions one under the other: all that was necessary was to find two phrases having 2 letters in common the appropriate distance in front of the "vonvon". To use this chart was thought by some cribsters to be unsporting and unaesthetic, but it was none the less a very useful document. The value of having cribbed the above messages was not, of course, only that we now possessed a crib which would break the day but also that the hexagram had been proved beyond doubt to be a correct fit - a valuable contribution to the Banburismus.
By the early months of 1942 depth cribbing had become a fairly highly developed art. The amount of dummy traffic was steadily decreasing and much of the cribbing had to be between genuine messages; this, of course, was much more varied, much wider in its scope, and required a far greater knowledge of what messages were likely to say. This knowledge was obtained by extensive reading of traffic and by the keeping of such useful records as lists of ships likely to be addressed on the various frequencies.
The various applications of depth cribbing were also developed and the amount of assistance cribsters were able to give to Banburists steadily increased. I will give one example of the growth of a "monster depth" such as warmed the cockles of a cribster's heart.
We start by noting that there are 2 messages about which we think we know something and which have trigrams H E X and H E N, that is to say that they started within 26 places of each other on the machine and it is therefore possible that we may be able to set them in depth.