This song, from The Beatles' 1967 album Sgt. Pepper's Lonely Hearts Club Band, was not a single until covered by Elton John, who took it to #1 in 1974. John Lennon also performed on Sir Elton's version. (I know it, but I won't spoil it.)
Yeah, i know, but to be honest i never really belived Lennon's story, and considering the group were experimenting with questionable substances at the time, i think it was just to placate the press.