Who was John Lennon's mentor?

Answer 1

His mother taught him banjo chords, which he used to play guitar at first (on only four strings). Paul McCartney later taught him proper guitar chords.

Quarry Bank headmaster William Pobjoy credited himself as a mentor for Lennon during his teen years, after The Beatles became famous. Lennon's boyhood friend Peter Shotton disputed this, in his Beatles memoir.