Arguably the world's first operational electronic computer. Although a special purpose machine, it has many of the features still found in computers today. The first Mark I first ran on 5th February 1944. Two significant changes to the SZ42 (Tunny code) immediately made breaking this cipher more difficult.These changes were entirely coincidental, no knowledge of the breaking was known to the enemy. By 1st June 1944 a more advanced Mark II was operational, the building team working through the night to get it running. It gave important information about deceptions employed for the D-Day landing. A total of 10 machines were built. The order for number 11 was cancelled by VE day. Colossus at 70, 5th February 2014: http://www.telegraph.co.uk/technology/news/10618866/Colossus-at-70-the-computer-that-helped-bring-down-Hitler.html Colossus: Breaking the German ‘Tunny’ Code at Bletchley Park. An Illustrated History: http://www.rutherfordjournal.org/article030109.html
From British Intelligence In The Second World War by F. H. Hinsley et al. Volume 3, Part I, appendix 2, p481-482 (Doh, posted two pages in wrong order!)
The women who cracked Hitler's code: Bletchley Park Wrens reveal their secrets http://www.express.co.uk/news/uk/459896/The-women-who-cracked-Hitler-s-code-Bletchley-Park-Wrens-reveal-their-secrets
Bill Tutte - born 97 years ago today, the man who broke the Lorenz SZ42 cipher machine. http://www.tnmoc.org/news/notes-museum/more-about-bill-tutte http://www.theguardian.com/news/2002/may/10/guardianobituaries.obituaries