The Newmanry History
Part of the General Report on Tunny(1945)
Codes and Ciphers
38 Page 294
and then to add them. Therefore whenever a few lines of a single flag were
completed they were torn off and given for entering to the computer in charge of
The time for making a combined flag was about 3 1/2 hours.
If the converged combined flag proved significant the Delta-X5 pattern was
taken through the rectangles and the resulting scores for each character sent to
Room 41 with the flag scores for each character of Delta-X5.
Results were recorded and further work was normally done in Room 41, unless
the key was issued to Colossus.
If the combined flag proved insignificant, all working and entering was
rechecked by the wheelsman and if no mistakes were found either:
(a) the key was abandoned
(b) a Delta-X4 flag was made,
(c) the key was issued to Colossus for convergence of a 150 x 150
rectangle in the hope that this might prove significant.
In view of the work involved in making a combined flag and the strain on
computers, experiments in making the flag mechanically started in 1945. These
were never successful enough to produce new operational technique and are
described in an appendix.