The 70th anniversary of the world's first electronic computer will be celebrated today by code-breaking veterans and their families.
Seven decades ago today, Colossus Mk I attacked its first message written in the complex code used by Adolf Hitler and his generals during the Second World War.
Colossus was built to speed up code-breaking of the sophisticated Lorenz cipher and is regarded as the world's first digital, electronic computer.
By the end of the war there were 10 functioning Colossi machines, which had a decisive impact on the war.
To mark the anniversary, Colossus veterans and their families will gather at The National Museum of Computing at code-breaking institution Bletchley Park where they will see a re-enactment of the code-breaking process from intercept to decrypt with a working rebuild of Colossus.