Hi Bleen
The reason I think it sounds more like Paul is it reminds me of his solo in Taxman
Wonderful bass lines in this song as well
According to my reference it was George. John played piano. It recounts an anecdote that the people in the studio revved George to turn his amp up.
But I agree it sounds like a Paul solo to me. More busy than melodic
Apparently this was the last recording session before Yoko made herself a fixture in the studio. It was by all accounts a happy session that went better than anyone expected.
John also tried to get this released as a single instead of lady Madonna.