40 O.B.

In 1932 Hugh Cleland Hoy raised more than a few eyebrows when his tantalising story of the shadowy yet extraordinary work undertaken by British Naval Intelligence in the First World War was published. Hidden away in the Admiralty and known only to a few, 40 O.B. was the silent offspring of the Senior Service; tirelessly decrypting German messages and working alongside the forerunner to Special Branch.