Paul McCartney interview from a 1968 BBC documentary.
The interview transcription can be found here.

“We’re the last people to know about our songs, because the pop world’s never heard the pop world as such. It’s like, if you look at a snapshot of yourself, you’re looking at what tie you were wearing or whether you were looking nice in the snapshot. But anyone else will just take the snapshot and say ‘Oh, that’s good. That’s a snapshot of Tony,’ you know. We’re always just thinking of ourselves as just happy little songwriters. Just little rockers, you know. Just playing in a rock group. But it gets more important than that, after you’ve been over to America… and you’ve sort of… got knighted.”

The Beatles - Hey Bulldog

“Help!” was written primarily by John Lennon, but credited (as all Beatles song written by either person) to Lennon/McCartney. Paul McCartney reports that he had a hand in writing the song as well, being called in “to complete it” in a two-hour joint writing session on 4 April 1965 at Lennon’s house in Weybridge. He later said that the title was “out of desperation”.