The pair married in 1962 but their relationship hit the rocks when the All You Need Is Love hitmaker began his torrid affair with Ono.
And his constant travelling made it impossible to salvage their marriage - he toured the world with bandmates Paul McCartney, Ringo Starr and George Harrison, while she stayed home and cared for their son JULIAN.
She says, "I was devastated. But there was no way I could talk to John because he just closed the door.
"He was cruel to me and awful to Julian. We'd been on a rollercoaster ride together but suddenly it was as though we were switched off - like a light."