Bletchley Park is famous for its role in regularly penetrating the secret communications of the German Enigma and Lorenz ciphers, with names such as Turing, Tutte and others. However, this talk by Ian Thomson is not only about Bletchley Park, but in particular about the work of the women. Their contribution to the success of Bletchley was an astonishing part of Britain's wartime history. They were certainly not 'just small cogs in a big machine'.