I Programmer was privileged to attend a special viewing of the new gallery for the rebuilt Colossus, the valve-powered computer, designed to break codes during World War II.

Bletchley Park, home to the World War II codebreaking efforts, has enjoyed a lot of attention this year due to the Turing Centenary. However, it  was also the location of the original Colossus, which played a role in decrypting teleprinter messages encoded using the Lorenz cypher. 

Although the Colossus machines were dismantled, a project to build a fully functioning version using original components has been successfully completed for the UK's National Musuem of Computing (TNMOC).

It is now possible to walk all around the Colossus Rebuild in the  newly expanded gallery and new information panels tell the story of the German Lorenz high-level coding machine and the British efforts to break the code, Y-stations and the undulators, the Heath Robinson, Tunny, the bedstead and of course the Colossus.

This in turn is the story of Tommy Flowers and the Post Office Research Station at Dollis Hill. The museum has now been donated Tommy Flower's wartime diary - kept strictly against the rules - which records some of the steps he took to create Colossus. Excerpts from the diary, and some of his other personal effects, will soon form part of an interactive display in the new gallery.

The gallery also has a video recording of Tony Sale, the originator and the driving force behind the Colossus rebuild, made just few weeks before his untimely death last year. In it Tony explains how Colossus was used the break the settings of the wheels of the 'Fish' (the British name for the Lorenz machine code), which took about 6-8 hours. The result was then used to set the Tunny machines to decode the messages. He also reveals that in fact two 'Colossi' did survive the war - and were used at GCHQ until 1961!

Another video commissioned for the gallery is of Capt. Jerry Roberts, the last surviving member of the 'Testery', talking about the complexity of Tunny messages and how Lorenz machine was able to decrypt them.

The fundraising appeal for the new gallery has reached two-thirds of its target and it is still looking for sponsors for its its virtual valves.