I think it was on the Anthology, but I'll have to check on that. At the end of 1966, after their sabbatical three months, they had recorded three songs, meant for a new album: Strawberry Fields, Penny Lane and When I'm 64. Brian Epstein wanted to release a single and asked George Martin what was available. He told Brian he had three songs, from which two of them were among the best The Beatles ever recorded. They decided to make it a double a-side. The single did not reach the #1 position and George Martin blamed himself for that. He thought it might have been better to promote whether SFF or PL as the new single, not both of them.