''I Feel Fine''by the Beatles, who does the lead ?

I Feel Fine (2:20)

Recorded: October 18, 1964
at Abbey Road, London, England

John Lennon - lead vocal, rhythm guitar, lead guitar
Paul McCartney - bass guitar, background vocal
George Harrison - lead guitar, background vocal
Ringo Starr - drums

Both?

Here's a link to more than you ever wanted to know about "I Feel Fine". I'm not sure who does the solo, but the opening guitar is Lennon.

I remember reading a long time ago that other musicians would occasionally sit-in and record with the Beatles; but never got mentioned. Clapton was one of them. Harrison would sit-in on other bands recording session and would never be mentioned, except when he used the name Angelo Mysteriouso (something like that). But in 1964, who knows? The lead guitar sounds more "seasoned" than what Lennon was capable of at that time.

As a follow-up, who does lead vocal in the original recording of 'Sunshine of Your Love' by Cream?

I know it is Jack Bruce, but have you listened to it with this question in mind?

Danger: This question can start quite the argument amoung many a know-it-all classic Rock 'expert'.