Jean Argles gave a fascinating talk about her experience during the war, working as a cypher operator for the SOE. She explains how her skills with a crossword puzzle was the indicator that got her recruited for the role. She was trained in the Cipher Department in Baker Street run by Leo Marks. They were instructed to change the bus stop they used on their way to work so that anyone watching could not tell where they were going, but one day had the schock of hearing the bus conductor calling out "Any more spies?" before ringing the bell!
It's great fun - and you can listen to it at http:/Bambuser.com/v/6457255#t=128s