"John and Yoko had got together and that was bound to have an effect on the dynamics of the group," McCartney shared with poet Paul Muldoon.
"Things like Yoko being literally in the middle of the recording session [were] something you had to deal with," he later added. "The idea was that if John wanted this to happen, then it should happen. There's no reason why not."
When Muldoon mentioned to the "Let It Be" singer that group was meant to be working when recording, McCartney added: "Anything that disturbs us, is disturbing."
"We would allow this and not make a fuss," he said. "And yet at the same time, I don't think any of us particularly liked it. It was an interference in the workplace. We had a way we worked. The four of us worked with George Martin. And that was basically it. And we'd always done it like that. So not being very confrontational, I think we just bottled it up and just got on with it."
McCartney then shared that ultimately, for the Beatles, spending time in the studio was part of their jobs.
"It was the idea of the Beatles, it was also just this straight, practical thing of 'This was our job.' This is what we did in life," he said. "We were the Beatles. That meant if we didn't tour, we recorded. And that meant if we recorded, we wrote."
"I didn't instigate the split. That was our Johnny," McCartney said of the band's 1970 breakup, when McCartney, Lennon, George Harrison and Ringo Starr decided to go their separate ways.
"I am not the person who instigated the split. Oh no, no, no," he added. "John walked into a room one day and said, 'I am leaving the Beatles.' Is that instigating the split, or not?"
McCartney added that he felt Lennon was "always looking to break loose" of the band, as he reflected on what "could have been."
"The point of it really was that John was making a new life with Yoko. John had always wanted to sort of break loose from society because, you know, he was brought up by his Aunt Mimi, who was quite repressive, so he was always looking to break loose," McCartney said of Lennon, who himself shared in a 1970 interview with Rolling Stone that he told McCartney he was "leaving" the group.