Quoted from Barry Miles' Many Years From Now:
p. 285: Living at Wimpole Street had meant that he was involved in the
family Asher diary, which inevitably meant he got up earlier than John and packed more into each day. John led a more
relaxed suburban life but if he went to dinner in London or to a club, living so far from town meant that returned home
very late. Paul would arrive at midday or the afternoon and wake him up, which was where John got the idea for 'I'm Only
Paul: 'It was a nice idea, there's nothing wrong with it. I'm not being lazy, I'm only sleeping, I'm yawning, I'm meditating, haVing a lay-in - the luxury of all of that was what it was about.' The song was written and arranged in one writing session, co-written but from John's original idea.
Though these were work sessions, they would also take time out for a friendly chat. The discussion that day was how to deal with pot and children, because they found themselves trying to hide it from Julian and keep him from seeing what they were doing. It was a problem for Paul because he had no children, but Julian was of an age when John had to decide how to deal with it. They agreed it was best not to roll up and smoke openly in front of him but to keep it as something they did in private.
For Paul, the most exciting thing that happened with 'I'm Only Sleeping' was during the recording rather than in the writing. They were taping George's guitar solo and the tape operator put the tape on tails out.
PAUL: It played backwards, and, 'What the hell is going on?' Those effects! Nobody knew how those sounded then. We said, 'My God, that is fantastic! Can we do that for real?' So George Martin, give him his due, being amenable to ideas like that, being quite experimental for who he was, a grown-up, said, 'Yes. Sure, I think we can do that.' So that was what we did and that was where we discovered backwards guitar. It was a beautiful solo actually. It sounds like something you couldn't play.