From Terry Cannon, Lewes, East Sussex, UK
Your fascinating article about deciphering historical documents written in code made me wonder where the code-breaking sources that must have been needed by the senders and recipients of these documents are (23 September, p 40). Have none been found? No worksheets where recipients struggled to “translate” what they were given? Are there no books with guidance on how to encrypt messages, or did each author invent their own method?
