BBC World Affairs Correspondent Emily Buchanan hears the little-known story of around 300 young men who were selected to learn Chinese at the start of their National Service and then sent to Hong Kong to eavesdrop on Chinese communications.
In the mid 1950s, with the Cold War raging and Chairman Mao's communists in power in China, the RAF began a top-secret programme to select and train a small group of National Servicemen to carry out intelligence work in Hong Kong.
For six years from 1955 about 60 a year spent 12 months learning Chinese in England before being flown across the world to monitor radio broadcasts from the highest peak on Hong Kong Island for six months before being demobbed.
Emily hears fom some of them about their time on a course which few had known about or chosen to do, and how it changed their lives.
They recall the intensive language lessons, life in Hong Kong, the work itself and what they have since learned about their role in the Cold War.
Some went on to work in intelligence, others formed the basis for a generation of professors of Chinese at British universities, and some never used their Chinese again.
But all recall how the often chance decision to select them for the language course changed their lives.
The story of the National Servicemen who were sent to eavesdrop on Chinese communications.