I attended a CAA Safety Evening some years ago at which one of the speakers was a CAA Surveyor. He talked about his work and how they found exactly the sort of things described by Julian. I stuck my hand up
"So you found aircraft that had Certificates of Release to Service that should not have been issued because the aircraft were not airworthy?"
"Yes, that's right."
"What action did you take against the persons who had signed the Certificates?"
"Airworthiness is the responsibility of the operator."
Sad but true.