Good grief (with a side order of citation needed)
"At the time there was a union rule that wouldn’t allow library music to be recorded in the UK. The unions were concerned that the music libraries would make many professional musicians redundant, so the musicians would go abroad to record most of the big arrangements. Sometimes, however, KPM would ‘cheat a little bit’ and secretly record some sessions in the KPM studios back in London.
“They always used to have a scam, they used to have a letter to say what the music was, in case the union rep came there and said: you’re doing library music! Robin always had this letter there from Pathe/Marconi, saying it was to do this specific music for their film in France.”"
(the Freewheelers theme was apparently a library track by Keith Mansfield called 'teenage carnival')