The first Colossus came into operation at Bletchley Park in January 1944. It exceeded all expectations and was able to derive many of the Lorenz settings for each message within a few hours, compared to weeks previously. This was followed in June 1944 by a 2,400-valve Mark 2 version which was even more powerful, and which provided vital information to aid the D-Day landings. By the end of the war there were 10 Colossus computers at Bletchley Park working 24/7.
