The Colossus at work at Bletchley Park in 1944. Image courtesy of Computer History Museum.

Developed at Bletchley Park to crack encoded German messages during World War II, the world’s first programmable digital computer – Colossus – returned to action on 15 November 2007 to mark the launch of the first part of the emerging National Museum of Computing.

The Cipher Challenge saw the public invited to intercept and decode Lorenz code transmitted from National Museum of Computing colleagues in Paderborn, Germany – alongside Colossus.

It was the first time that Colossus had been used since Prime Minister Winston Churchill ordered the destruction of the top-secret machine in 1945 following the Allied victory that it helped achieve.

The 10 Mark II Colossus machines made enabled code breakers at Bletchley to decipher top-secret communications sent by the Nazi high command, leading to the war being shortened by many months and saving thousands of lives.

Over the past 14 years, experts have painstakingly rebuilt a Colossus Mark II computer using stolen design plans and by gleaning information from those involved in the creation of the original.

The team using Colossus managed to decipher the message just after lunch on 16 November, but were reportedly beaten to the task by an amateur cryptographer from Germany, Joachim Schuth.

At the same time as Colossus cranked through the messages a separate team used a virtual Colossus on a laptop to read the scrambled messages. That too beat Colossus and deciphered the message mid-morning on Friday.

For more information, visit The National Museum of Computing:  
www.tnmoc.org.uk.