Q&A: Tony Sale, the man who rebuilt Colossus

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Bletchely Park is widely recognised as the home of computing as we know it today. Back during World War II (WWII), dedicated British code breaks worked there tirelessly to break German code and help eventually win the war.

At the heart of such deciphering efforts in reading encrypted codes - encrypted by the German Lorenz SZ40/42 machine - were the Colossus machines. These mammoth computers were the first programmable ones of their kind. Complex calculations were carried out almost effortlessly by the vacuum tubes used.

We have engineer Tommy Flowers and his team including Allen Coombs, Sid Broadhurst and Bill Chandler to thank for the birth of Colossus.

And Tony Sale and his team to thank for its rebirth so many years later. For in 1991, Sales and fellow volunteers embarked on a project to reconstruct Colossus to ensure its rich heritage and story live on.

How long have you spent working on this mammoth rebuild project?

It's taken about 15 years for us to rebuild. It was built from eight black and white photos and some fragmented circuit designs. It's been reverse engineering, squared. And bloody difficult! But it's been very successful.

It's taken 15 years of my life so it's very important as it was the first electronic programmable computer... It has 2.5 thousand valves and is switched logic. It's a bit like your mobile phone.

How does it work? Wasn't it ground-breaking in its day?

I've got a Pentium 2 computer and on that it's running a virtual Colossus and on that it takes the same amount of time to break a cipher as that machine did and does now.

It was very successful in breaking the German's Lorenz cipher. It can take up to six hours to find all the settings, but that was a remarkable achievement.

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