Today, Feb 5th, is the 70th anniversary of the first operation of Colossus. Colossus was the worlds first programmable digital electronic computer. It was built in the Second World War at Bletchley Park so as to enable the efficient breaking of the German Lorenz cipher traffic. The machine was built by the Post Office engineer Tommy Flowers, and utilized the amazing cryptanalytic breakthrough of Bill Tutte. A number of Colossi were built in the war but most were destroyed on the German surrender, with only two being passed to GCHQ for future work. The secret of the existence of the Colossus only came out in the 1970s. Since that time a replica of the Colossus has been built at The National Museum of Computing; with most of the work being done by a Tony Sale. You can now see the Colossus at the museum.
Today was a special day, and a special event was held at the museum. A large number of guests turned up, including some of the original operators to see the entire breaking of Lorenz operation in action. First a message was received at a replica Y Station. Then the received data was converted to paper tape and passed to some WRENs for entering into Colossus. Colossus then found the wheel settings for the Lorenz cipher. Finally, the message was decrypted using the Tunny machine.