I came across this while looking for something else on YouTube, as you often do! It’s a 1979 BBC documentary outlining the work of the ‘VIs’ - Voluntary Interceptors - who were recruited by Military Intelligence in the Second World to listen to German radio traffic.
It’s an ‘old school’ documentary in that it is presented by someone who has expertise in their field, it treats the audience with intelligence, and when broadcast would have genuinely informed an audience of something new. Even better, the contributors are people who were actually there and took part.
The presenter is René Cutforth, who was a veteran of the Second World War and taken prisoner in North Africa in 1941. He had a long broadcasting career with the BBC until his death in 1984.
I hope you get as much from it as I did. Do let me know in the comments.