day to day but repeated from month to month). This work had been started by Wylie and passed on by him to Ashcroft who did a great deal of patient and valuable work on all forms of short signals particularly W W's and B bars.
19. We were still however a long way from being able to use the W W's for breaking when, in October 1942, the Wetterkurz schluessel complete with indicator tables was captured in the Mediterranean from U-559. This pinch enabled us to read 8 days traffic in November, 25 in December, all January and February except Jan. 19/20th and February 28th and March 7th and 8th. On March 10th the book was changed and the great days of W W's were over.
20. Once the book had been captured things were fundamentally fairly plain sailing although there were a good many practical snags. Archer's section went onto 3 shifts as the operational importance of their work was of course tremendously increased by the pinch and constant and close liaison was maintained between us; we were always more than satisfied with the help they gave us and hope that they were equally happy about our cooperation.
21. As the whole subject of W W's is intrinsically very interesting in a general way and not particularly complicated technically it is worth giving an (imaginary but typical) example quoted by Ashcroft in a comprehensive write up of the subject.
22. (1) Instructions from control. "U-531 and U-668 are to send W W's between 0020 and 0400 tomorrow morning." Naval section (N.S. IV) estimate of positions
U-531 (signature LX) 53 x 33.
U-668 (signature PJ) 48 x 21.
[U-boats had two letter signatures known to us]
(2) Archery decodes spotted as being derived from W W reports :