As young women growing up in wartime Britain, Jean Nissan and Pat Davies led extraordinary lives.

Pat was stationed at various locations along the British coastline and her job was to intercept coded German U Boat messages. These were then sent to Bletchley Park, where the likes of Jean and her colleagues attempted to crack them.

It is only recently that the secret work of the code breakers at Bletchley Park has been revealed. Led by Commander Denniston, the likes of Alan Turing and Dilly Knox devised automatic machinery to help with decryption, culminating in the development of Colossus, the world's first programmable digital electronic computer.

Everyone who worked there signed the Official Secrets Act – and many have since passed away. But now Jean and Pat, both in their 90s, get to tell their incredible stories.