In 1943 Tommy Flowers a General Post Office research engineer designed Colossus based on Alan Turings work on crypto analysis and computer theory and plans by Max Newman funding it with his own money and assisted by Sidney Broad Hurst, William Chandler and later Allen Coombs.

Colossus had no memory. It was programmed by plug boards. Designed specifically to break the Nazi Lorenz cipher used in WW2 by the German high command, including Hitler himself. Encrypted messages were fed into the machine by a continuous loop of paper tape.

Kept top secret for 30 years after WW2, with all documentation and machines destroyed or dumped down mines besides two kept at GCHQ till the 60's, Colossus was not included in the official record of computing history for decades leaving the ENIAC, the worlds first general purpose electronic computer to claim to be the title of worlds first electronic computer also.

All plans and hardware were destroyed or recycled. Tommy Flowers himself remembers taking the schematics and other documents to watch them burn, something he later described as a terrible mistake.

Later in the 70's Processor Brian Randell began uncovering what was left of any information to do with the existence of Colossus. Helped by the publication of Group Captain Winterbotham's book *The Ultra Secret* and a few surviving photographs of the Colossi helped to bring Colossus into the light.

A surprisingly good amount of information about the machine managed to survive, much found in notebooks and unearthed all over the USA, allowing Tony Sale and his team to build a working reconstruction of a Colossus MK2 between 1993 and 2008. Dr Arnold Lynch, the original designer of Colossus' optical reader was still alive (died in 2004) and was able to redesign the critical component to his original specification for the reconstruction. Tommy Flowers himself was instrumental with assistance in the reconstruction before he passed away in 1998.

The reconstructed Colossus resides functional and demonstrated to the public in the original home of Colossus Number 9 in The National Museum of Computing, H Block, Bletchley Park, Milton Keynes, Bucks, England.

Tommy Flowers returned to Dollis Hill working for the GPO, having built Colossus with his own money he was left in debt, a government grant of £1000 failed to cover the full cost.