"John walked into a room one day and said, ‘I am leaving The Beatles,’" McCartney said. "I wanted it to continue."
The previously unseen video features the Beatle working on "Give Peace A Chance" days before the song was recorded.
The former Beatle's upcoming book, “The Lyrics: 1956 to the Present,” will trace his life through 154 songs.
Paul McCartney and Ringo Starr posted tributes marking the 40th anniversary of the rock legend's death.
Mark David Chapman, 65, is serving a 20-years-to-life sentence for the 1980 murder of the legendary Beatle.
Kirchher met the Fab Four in Hamburg and shot some of the earliest and most striking images of the band.
Natalie Portman, Mark Ruffalo, Will Ferrell and others join the Instagram video because "we're all in this together," the "Wonder Woman" star said.
The Beatles legend revisited his relationship with John Lennon on "The Late Show."