Veterans gather for the 70th anniversary of Colossus, the world’s first electronic computer

Colossus veterans and their families gather today at The National Museum of Computing located on Bletchley Park to celebrate the 70th anniversary of Colossus, the world’s first electronic computer. They will see a re-enactment of the code-breaking process from intercept to decrypt with a working rebuild of Colossus.

On 5 February 1944 Colossus Mk I attacked its first Lorenz-encrypted message, the highly sophisticated cipher used in communications between Hitler and his generals during World War II.

Designed by brilliant British telephone engineer Tommy Flowers, Colossus was built to speed up code-breaking of the complex Lorenz cipher. By the end of the war there were ten functioning Colossi and they had a decisive impact in shortening the war and saving countless lives.

Colossus was the first electronic computer, but news of its existence was kept top secret for 30 years because of the sophistication and sensitivity surrounding the encryption it had helped to break.

The statistics of Colossus are astounding. It occupied the size of a living room (7 ft high by 17 ft wide and 11 ft deep), weighed five tonnes, and used 8kW of power. It incorporated 2,500 valves, 501 of which are thyraton switches, about 100 logic gates and 10,000 resistors connected by 7 km of wiring. Reading 5000 characters per second (faster than anything ever produced commercially), Colossus found the start wheel positions of Lorenz-encrypted messages to enable the decryption of 63 million characters.

Typically, it took Colossus up to four hours to establish the start wheel positions of messages. It is often surmised that the Allies might have been reading some of the decrypted messages even before they reached German High Command. By the end of the war, 63 million characters of high-grade German messages had been decrypted by the 550 people working on the ten functioning Colossi at Bletchley Park.

As the first electronic computer, the legacy of Colossus lives on. It had to be kept secret for 30 years, but many of those who worked on it went on to build other computers and technologies, using the knowledge that it was possible to build reliable machines of such complexity.

Tim Reynolds, Chair of The National Museum of Computing, said: “The achievements of those who worked at Bletchley Park are humbling. Bill Tutte’s ingenuity in deducing out how the Lorenz machine worked without ever having seen it, the skill of those in the Testery who broke the cipher by hand, and Tommy Flowers’ design of the world’s first electronic computer Colossus to speed up the code-breaking process are feats almost beyond comprehension.

“The working Colossus rebuilt by the late Tony Sale and his team provides a mesmerising start to our story of the history of computing at The National Museum of Computing. It fascinates people of all ages and we see on a daily basis the inspiration that it provides to school groups who visit the Museum.

“February 5 will be a proud day for the Museum to host the Colossus and Tunny veterans who are able to make the journey today. This day is in honour of all the men and women who worked on breaking the Lorenz cipher.”