Paul McCartney actually wrote this song long before
Sgt. Pepper was released. He waited until 1966, however, because that was the year his
father turned
64.
An interesting musical fact (revealed in Yellow Submarine) is that this song's tempo is 64 beats per minute.
It was also, like some other Beatles songs, recorded in a different key than it was eventually mastered at; in this case, it was recorded in C and appears on the album in Db. The speeding up on the tape may have been to change the feel of the piece (to make it more 'earnest'), to make it easier to read (the key of C has no sharps or flats), simply to bring the tempo to the aforementioned speed, or any combination of the above.
some help from http://rmb.simplenet.com/public/files/awp/wisf.html