Professor Brailsford returns to the subject of why Colossus was built. The professor's notes: http://www.eprg.org/computerphile/lorenz-combined.pdf Bletchley Park Playlist:    • Bletchley Park (Colossus) Playlist   Professor Brailsford used the book "Colossus" by B. Jack Copeland and others (Oxford University Press, 2006). Also recommended are chapters 18 and 19 from : "The Bletchley Park Codebreakers" by R. Erskine and M. Smith (eds.) Biteback Publishing 2011 https://www.facebook.com/computerphile https://twitter.com/computer_phile This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: https://bit.ly/nottscomputer Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com/