April 21, 2016
Room 40 and WWI Cryptoanalysis
April 21, 2016
Information from the Institution of Engineering and Technology and Wikipedia.

Image from Paul Gannon, "First World War technology: Room 40 secret intelligence unit," Engineering and Technology Magazine, May 19, 2014, http://eandt.theiet.org/magazine/2014/05/before-bletchley.cfm, accessed April 21, 2016.