It is now 50 years since the Nato alphabet, in common use by aviators, the police, Ryanair booking clerks etc, was devised in its present form. The original intent was to have a system of linguistic purity that would avoid some of the catastrophic misunderstandings arising from miscommunications during the Great War. Here, the story of this phonetic alphabet, including testimony to its usefulness, is told. Alongside historical evidence and linguistic analysis, there are also snatches of eavesdropped sound from air-control conversations with aircraft, interviews with police officers (remember Zed Victor One?), and secrets of Army signals operatives Working in code. Producer David Roper