After the capture of code books from the German naval trawler Krebs in March (?) 1941, the teams at Bletchley Park were able to decoded the U-boat signals for February 1941. Does anyone know if these decodes have survived and, if so, where they are?
The National Archives under reference DEFE 3. You can download digital copies for free as part of the Digital Microfilm Project, and they take some time on a slow internet connection. The series description gives some useful information.
The earliest file I could find on Ultra based on radio signals from U-Boats was DEFE 3/20. The original file series was entitled ZTPG 1-999 covering the dates June 16-24, 1941. I ordered the file yesterday by giving my email address and requested a download from the "receipt" ( there is no payment involved ). The total download of the file appears to be 484 Mb and is presented for download in two parts in pdf. file format. I gave up waiting fairly quickly because my internet connection, allegedly good, cannot cope with a download of over 200 Mb during primetime entertainment online hours. Good hunting.
I found some of the February signals in DEFE3/1. Unfortunately the first 60 or so were from 26 Feb 1941 onwards and I am interested in 23 - 25 Feb particularly. Like you I gave up!! Anyway, thanks again. Roy