Back in London, at the piano in his Cavendish Avenue bachelor pad, Paul played it for John and Yoko. When he got to the line “The movement you need is on your shoulder,” he told them, “I’ll change that, it’s a bit crummy.” John replied, “That’s the best line in it!” John heard this new tune as Paul cheering him on in his romance with Yoko. “I took it very personally,” John told Rolling Stone in 1968. “‘Ah, it’s me,’ I said. ‘It’s me.’ He says, ‘No, it’s me.’ I said, ‘Check. We’re going through the same bit.’ So we...