Conversation:

Does anyone know when the word "Radar" ceased to be Top Secret. My Grandfather who I have just discovered to be an RAF Flying Officer, whe he was 45, spent his WW2 lecturing about Radar, My Grannie told a tale of the time when he received a Top Secret letter afte a lecture, which on deciphering said, effectively,"Top Secret, the word Radar, is no longer Top Secret." This of course begs the question as to what he called it before then! Lastly do all "Flying Officers Fly? Thank you.