No one has ever been able to ...

No one has ever been able to discover how they [cats] make this subtle sound, and what is more, no one ever will. It is a secret that has endured from the very beginning of the time of cats and will never be revealed.
 Paul Gallico

Quotes from the same author

No one can be as calculatedly rude as the British, which amazes Americans, who do not understand studied insult and can only offer abuse as a substitute.
 Paul Gallico