John Lennon's son felt "cast aside" when he embarked on a relationship with Yoko Ono

Julian said: "Suddenly my dad literally disappeared off the face of the planet. At least, that's how it seemed to me.

"He and Yoko Ono were deeply and publicly in love. And I felt as if my mum and I had been cast aside."

Julian, now 56, felt grateful that his dad's bandmate Sir Paul McCartney didn't "forget" about him.

He added: "Not everyone forgot about us, though. Paul wrote Hey Jules after dropping in to check how my mum and I were doing. (Obviously, the title of the song changed to Hey Jude)."

The 'Saltwater' singer didn't speak to his dad - who was shot dead in 1980 - for almost a decade but credits his "gentle" mother for helping them repair their relationship.

He told Observer magazine: "Maybe 10 years passed during which my dad and I barely spoke. I was very angry about how he left the family.

"It was thanks to my mum that we started having conversations again. She was such a gentle soul, never vindictive in any way, shape or form. She always wanted me to have a relationship with him."

Julian still strives for "forgiveness and understanding" towards his late father and holds his memory "dear", though he can't "forget" John's behaviour towards Cynthia.

He said: "I try to remember my dad as fondly as possible. I strive for forgiveness and understanding in that area of my life, for the difficult times he put my mum and me through. I loved her more than anything and can't forget how poorly he treated her.

"But our relationship was getting better before he died. He was in a happier place. He wanted to reconnect, not just with me but with the rest of his family. He never got a chance to do so. Even now, almost 40 years after he died, I hold my father's memory dear."