The Colossus computer was created during WWII to decipher critical strategic messages between the most senior German Generals in occupied Europe. To mark it's 80th anniversary GCHQ has released new photographs relating to Colossus.

The UK government kept the very existence of the code-breaking Colossus computer a closely guarded secret for decades, finally revealing its pivotal importance in the defeat of Hitler and the Nazi regime in the early 2000s. After the Second World War eight out of the ten machines that had been built at Bletchley Park were destroyed and the remaining ones, plus all their documentation, were handed over to GCHQ where they were still in use until the early 1960s.

In its announcement marking the 80th Anniversary of Colossus, GCHQ states: 

The release of these images sheds new light on the genesis and workings of Colossus, which was over two metres tall and considered by many to be the first ever digital computer.

The set includes a photograph of a letter dated 1 March 1943 by Max Newman, head of the cryptanalysis section at Bletchely Park. A routine progress report of the code-breaking effort using Tunny and Sturgeon, this letter contains the first reference to  the idea that would ultimately result in Colossus:

Flowers, of the P.O., has produced a suggestion for an entirely different machine, in which the message, and the wheels to be compared with it, would be set up on valves, by means of relays, This would involve 400 or so valves and about 2500 relays.

One of the "new" photographs will already be familiar to readers of articles on this site. It is of Colossus in operation at Bletchley Park but with annotations to provide information about parts of the machinery:

This photograph is a hardly legible circuit diagram: 

Lack of documentation was one of the problems faced by the project to reconstruct a fully working replica of Colossus. The initiative came from Tony Sale, co-founder of The National Museum of Computing who had gathered snippets of information about the machines in the 1970s and 1980s. The rebuild was based on eight photographs of Colossus taken in 1945 and a few circuit diagrams kept by engineers who had worked on the original computer. Work started in 1994, and thanks to the efforts of Sale and his team of dedicated volunteers, was completed in 2007 and since 2012 has been housed in TNMOC's  new extended Colossus Gallery allowing visitors to see it in action. 

Tony Sale (1931- 2011) and the rebuilt Colossus 

Two of the newly released photographs are dated 1963 and show Colossus at GCHQ. They clearly reveal the size and complexity of this historic computer.

More Information

GCHQ Celebrates 80 Years of Colossus

Colossus Gallery at TNMOC

Related Articles

Codebreaking and Colossus

The New Colossus Gallery

Colossus Re-enactment To Mark 70th Anniversary

Block H and Colossus Revisited In Virtual Reality

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