January 2024

Eighty years ago, in January 1944, the first Colossus computer was delivered to Bletchley Park. This machine and the nine that followed it have acquired legendary status within the story of World War Two codebreaking. The machines have also been described as the world’s first large-scale electronic digital computers – direct precursors of the digital world in which we live today.

But in 1944 the computer age still lay far in the future. These machines were built for a specific and vital purpose, to assist with the breaking of the wireless messages of Germany’s senior commanders, enciphered using the Lorenz cipher machine and known at BP as ‘Tunny’.

What role did Colossus actually play in the breaking of Tunny? The Colossus machines were members of a wider family of machines, and the Newmanry – the department in which they operated - was only one of several teams at Bletchley Park, all of whom were crucial to the successful breaking of the cipher.

In this ‘It Happened Here’ episode, Bletchley Park historians Dr Tom Cheetham and Dr David Kenyon are here to place ’Colossus in Context’ and examine where exactly these machines fitted into the effort to break Tunny.

Many thanks to Dr Ben Thomson for voicing our archival documents.

Image: ©Crown. Reproduced by kind permission, Director, GCHQ

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