One rare photograph features a letter tracking the progress of the work being done to decipher communications between senior Nazis. The letter includes the words “Flowers of the P.O. has produced a suggestion for an entirely different machine” – a reference to famed codebreaker Tommy Flowers’ idea that would ultimately result in Colossus.
Another part of the letter reveals the high-level communications Colossus was intercepting, including, “rather alarming German instructions.”
Anne Keast-Butler, Director GCHQ, said:
Technological innovation has always been at the centre of our work here at GCHQ, and Colossus is a perfect example of how our staff keep us at the forefront of new technology – even when we can’t talk about it. The creativity, ingenuity and dedication shown by Tommy Flowers and his team to keep the country safe were as crucial to GCHQ then as today. I’m thrilled to be celebrating the 80th anniversary of this computer and honouring those who worked on it.
Engineers and codebreakers who had worked on Colossus were sworn to secrecy and unlike the well-known Bombe Machine which broke the Enigma cipher, existence of this vital piece of machinery was kept from the history books for almost six decades. After the Second World War eight out of the ten machines were destroyed and Flowers was ordered to hand over all documentation on the Colossus build to GCHQ. This was partly because the technology was so effective, its functionality was still in use by us until the early 1960s.
Secrecy was woven into the workings of Colossus from the beginning. Overseen by Tommy Flowers - the engineer who designed it - many of the experts working on the computer had no idea what they were helping to build until it was installed at Bletchley Park. Once there, only a small group – all sworn to the Official Secrets Act – knew about the work being done with Colossus.
Bill Marshall, Former GCHQ engineer said:
“I worked as an engineer on Colossus for a year during the 1960s. I had just signed the Official Secrets Act and knew nothing about GCHQ but was offered ‘interesting work’ which I believed would be dealing with telegrams for a government department.
I was told very little about the machine I was working on – what the machine was actually doing was not for me to know. My job was to repair it as necessary, using just a few circuit diagrams and no detailed user handbook. It wasn’t until much later that I found out that the several of the systems and detailed design information were supposedly destroyed at the end of WWII.
I’m very proud to have been involved with Colossus even in just a small way, and we should all be proud of what was achieved in the name of national safety and security.”
Andrew Herbert OBE FREng, Chairman of Trustees at The National Museum of Computing said:
“Colossus was perhaps the most important of the wartime code breaking machines because it enabled the Allies to read strategic messages passing between the main German headquarters across Europe. This is one of the many reasons we’re so proud to have a fully working reconstruction of a Colossus code breaking machine on display at The National Museum of Computing at Bletchley Park.
From a technical perspective, Colossus was an important precursor of the modern electronic digital computer, and many of those who used Colossus at Bletchley Park went on to become important pioneers and leaders of British computing in the decades following the war, often leading the world in their work. We are proud to join with GCHQ in celebrating this significant date in the Colossus legacy.”
Ian Standen, CEO of Bletchley Park, said:
“The development of the Colossus machine was a huge advancement in Bletchley Park’s codebreaking efforts helping the Allies break one of the most complex ciphers of WWII. Thanks not just to Colossus, but the pioneering post-war computing work of codebreakers like Alan Turing, Max Newman, Donald Michie, and Jack Good, Bletchley Park is considered a birthplace of modern computing.
This legacy was key in Bletchley Park being chosen as the host venue for the world’s first Artificial Intelligence Safety Summit in November 2023. It is therefore right and proper to mark the 80th anniversary of the deployment of this pivotal piece of technology.”
Despite using around 2,500 valves and standing at more than two metres tall, Colossus is considered by many to be the birth of modern-day computing and is still thought of today as the first digital computer ever made. Experts who worked on the code-breaking computer went onto to create the Manchester Baby built at the University of Manchester in 1948 – putting Manchester at the centre of a global computing revolution.