The Beatles felt threatened when Yoko Ono joined John Lennon for recording sessions, according to Paul McCartney.
Yoko has often been blamed for breaking up the Fab Four, but the bandmates have always played down the gossip, insisting they were destined to split.
Now, in a candid interview with Rolling Stone magazine, McCartney admits it was weird when Lennon's partner started joining him in the studio, because up until that point, girls had always stayed away.
"(We were) threatened," he says. "(She was) sitting on the amps.
"Most bands couldn't handle that. We handled it, but not amazingly well, because we were so tight. We weren't sexist, but girls didn't come to the studio; they tended to leave us to it.
"When John got with Yoko, she wasn't in the control room or to the side. It was in the middle of the four of us."
McCartney realised any resistance was "something I had to overcome".
In the new interview, Paul also addresses chatter about a possible Beatles tour with the only other surviving member of the group, Ringo Starr, admitting such a trek "might be complicated".
He explains, "I don't think either of us have ever thought why do it, or why not. It's just that our roads are parallel, with intersections and diversions."
But he'll always be a fan of his former Fab Four bandmate, adding, "He's a great drummer, man. That's the thing about Ringo. He has a feel that nobody else has."
McCartney is currently on tour - his next date is in Washington, D.C. on Wednesday (10Aug16). He's also on the bill for the inaugural Desert Trip festivals in California in October (16).