One thing Bobby does not say in this clip, but which he told me on several occasions, is that the guitar riff was itself inspired by a riff in Dizzy Gillepsie's Manteca. Bobby loved jazz and his long-term fans will remember him opening his shows with Thelonious Monk's Straight No Chaser, using the Miles Davis arrangement. here is a clip of Dizzy playing Manteca.
Now let us listen to the full original V-Tone recording of Watch Your Step.
I will let you fine folk go to youtube on your own to listen to The Beatles. Incidentally, John Lennon is also said to have noted that not only I Feel Fine, but also Day Tripper were inspired by Watch Your Step.