Paul McCartney had the progression and melody kicking around to I Will for quite some time before he came up with what he considered acceptable lyrics. I have to say the end result is way more than acceptable. The original recording featured Paul playing two guitar parts behind his vocal.
This lesson includes a Campfire Version, the way Paul plays it now in concert, as well as a Fingers & Fills segment where the second guitar part is incorporated into the accompaniment. That part is significantly more difficult that the solo version but should be fun for some intermediate players to tackle.