Pattie Boyd explains in her autobiography "Wonderful Tonight":
One night in December 1969 I took my 17-year-old sister Paula to see Eric play in Liverpool. Paula was very pretty and a bit of a wild child, and that night Eric fell for her. After the show we all went to a restaurant and everyone was quite drunk and raucous. When the rest of us went back to the hotel, we left Eric and Paula dancing.
The next night Eric was playing in Croydon and again Paula and [Pattie] went to watch, and again there was a wild after-show party, this time at Eric`s Italianate manor house, Hurtwood Edge in Ewhurst, Surrey. Soon after, Paula moved in with Eric.
In March 1970, George and [Pattie] moved into a new house. (...) One morning shortly after moving in, a letter arrived for [Pattie] with the words `express` and `urgent` written on the envelope. (...) In small, immaculate writing, with no capital letters, [Pattie] read: `dearest l,`as you have probably gathered, my own home affairs are a galloping farce, which is rapidly degenerating day by intolerable day . . . it seems like an eternity since i last saw or spoke to you!please do this, whatever it may say, my mind will be at rest . . .all my love, e.`
That evening the phone rang. It was Eric. `Did you get my letter?` he asked.
By this time [summer 1970] Paula had gone. She had been with Eric in Miami when he was recording Layla and knew instantly it was about [Pattie]. She had always had a suspicion he was with her only because she was the next best thing to [Pattie] and [Pattie] was unobtainable. Hearing Layla confirmed it.
[Paula] had been seriously in love with Eric, but he destroyed her pride, her self-esteem and her confidence, which were already fragile.