After reading Brian Mooney's letter in the June issue, my gut told me he is correct about who is "singing the fade at 6:48".
I just listened. If I have it right, we're talking about the "well eh-na-na" vocal adlib. While I can see someone thinking this is John, to my ears it is Paul (in his "rough" voice) all the way, not just here but throughout the tune.
I suppose this can be "verified" if anyone has a copy of "Recording The Beatles", which I do not as yet.
P.S. Here's one that threw me: I was listening to the "Please Please Me" CD earlier this afternoon. The first tune is "I Saw Her Standing There".
John? Or Paul?