When the world's greatest pop band played their final public concert in January 1969, there were no tickets or posters printed. When John Lennon, Paul McCartney, George Harrison, and Ringo Starr emerged at lunchtime from the headquarters of their own company, Apple, five stories above London's Savile Row, only a select group of people knew what the hell was happening. The rooftop concert was one of the Beatles' most spontaneous acts.