Colossus Rebuild Project 

An authentic rebuild of the world's first semi-programmable computer.

Now viewable in Block H. Please call 01908 640404 before travelling for availability.

Please be aware that the Colossus Rebuild Project will be closed for refurbishment from 30th January 2012 - 5th March 2012. The Tunny Gallery will still be open. During this period there will be no charge for the Colossus & Tunny galleries. Sorry for any inconvenience this may cause.

The first machine designed to break the Lorenz was built at the Post Office research department at Dollis Hill and called ‘Heath Robinson’ after the cartoonist designer of fantastic machines. Although Heath Robinson worked well enough to show that Max Newman’s concepts were correct, it was slow and unreliable.

Max Newman called in the help of Tommy Flowers, a brilliant Post Office Electronics Engineer. Flowers went on to design and build ‘Colossus’, a much faster and more reliable machine that used 1,500 thermionic valves (vacuum tubes). The first Colossus machine arrived at Bletchley in December 1943. This was the world’s first practical electronic digital information processing machine - a forerunner of today’s computers.

Lorenz had to be cracked by carrying out complex statistical analyses on the intercepted messages. Colossus could read paper tape at 5,000 characters per second and the paper tape in its wheels travelled at 30 miles per hour. This meant that the huge amount of mathematical work that needed to be done could be carried out in hours, rather than weeks.

Mark I Colossus was upgraded to a Mark II in June 1944, and was working in time for Eisenhower and Montgomery to be sure that Hitler had swallowed the deception campaigns prior to D-Day on June 6th 1944. There were eventually 10 working Colossus machines at Bletchley Park.

To see the Colossus in action click here

To Find out more about the Colossus rebuild please visit the Codes and Cipher website by Tony Sale