"I remember being out in the garden with Eric at one point," Boyd said. "And then George appeared from nowhere and said to Eric, 'What are you doing? What's happening?' And then that's when Eric said, 'I'm in love with your wife.'"
Boyd felt she was being forced into making a decision that would stay with her for the rest of her life.
"I just wanted the earth to swallow me up," she said.
Harrison asked who she was going home with. Boyd chose her husband.
"You see, I'm a Pisces," Boyd said. "In astrology that's two fishes swimming in different directions. So I am typical, being pulled one way or the other. It's a really bad sign to be in this situation."
Clapton didn't let her decision phase him. The next time he saw Boyd, he held up a vial of heroin, vowing to take it if she didn't run off with him. Again, she refused.
"The result of that was that he sunk into a sort of heroin addiction for about four years … three, four years," Boyd said. "And that was it."
Meanwhile, Harrison began to withdraw. After the Beatles broke up, Boyd said he became distant and distracted.
"We were just really unhappy with each other. And I think when you're unhappy … you behave badly," she said.
According to Boyd, "badly" meant infidelity, drinking and drugs, not to mention one particularly hideous scene, when Harrison was caught having an affair with Ringo Starr's then-wife Maureen.
"Maybe he was reacting against what Eric had said to him," she said. "The whole thing was a mess."
Clapton kicked heroin, but he couldn't let go of Boyd. He continued his pursuit, and in the summer of 1974, Boyd decided to split with Harrison.
"I'd sort of had enough. I couldn't see any way out of this situation. It was an untenable time. And I just didn't want any more of it," Boyd said. "At the end of the day, I just had to take the bull by the horns and say, 'Right, I'm making a decision. Am I gonna stick to it?' And that's what I did."
Boyd stayed with Clapton for 14 tumultuous years. They married in 1979 and divorced in 1988 after Clapton revealed another woman was pregnant with his child.
"That relationship I think was all about extremes. Loads of heartache, and loads of fun, and you know, joyous times," she said.
Their happier times inspired another song that Clapton wrote as Boyd dressed for an evening out. He called it "Wonderful Tonight."
"It makes me feel flattered that songs … beautiful songs were written for me. I can't take it on board personally," she said. "I'm trying to receive it in a gracious manner, but it's kind of too overwhelming."
Remarkably, up to his death in 2001, Harrison remained on good terms with Clapton. They even spent Christmas together on the very year Boyd left Harrison.
"George was actually horrified, really, because I was eating turkey, and we were vegetarians," Boyd said. "So I'd changed."
So who, in the end, was the great love of her life? "I feel that George is with me forever," Boyd said. "So I suppose I'll have to say that George is the love of my life."
Pattie Boyd's long-lived love affair with photography provided a one-of-a-kind peek into an unforgettable era. You can view her photographs at the Morrison Hotel Gallery.