It was the showbiz breakup that set the stage for a decades-long music career and entry into the Rock and Roll Hall of Fame. Now, the singer Cher has revealed what finally made her leave Sonny Bono and strike out on her own: the Hollywood legend Lucille Ball reminded her she was the talented one.

The singer told BBC One’s Graham Norton Show she resolved to break up the onstage and marital union unless Bono agreed to an equal split. But she still needed a final push to take that step. “I didn’t know what to do and leaving was a hard thing for me. [Lucille Ball] was on television and part of a couple [with Desi Arnaz], so I went to her, and she said: ‘Fuck him, you’re the one with the talent.’”

Sonny and Cher met in a coffee shop in 1962. He was a successful songwriter and she was an aspiring singer. They soon married, and would form one of the most influential showbiz couples of their era.

But Cher learned Bono had effectively made her his employee, rather than his partner, in their professional life; setting up a company named Cher Enterprises of which he was the majority shareholder. Cher, therefore, had been subjugated to Bono professionally.

“We had a strange relationship, and when I learned that he and his lawyer owned everything and I was just an employee, I said I wanted to be 50-50 partners, otherwise I would walk,” she told Norton in an episode due to air on Friday, as she promoted her autobiography The Memoir, Part One.

“I didn’t want to leave, but I couldn’t be under that contract – I had no money. There is no bitterness towards Sonny. I was angry with him, but I just couldn’t be mad at him. We were friends until he died.”

Cher has previously told Vanity Fair that Bono treated her “more like a golden goose than like his wife”. In 2010, she told the magazine: “I forgive him, I think. He hurt me in so many ways, but there was something. He was so much more than a husband – a terrible husband, but a great mentor, a great teacher … If he had agreed to just disband Cher Enterprises and start all over again, I would have never ever left. Just split it down the middle, 50-50.”

She added that Bono had told her when they were together: “One day, you are going to leave me. You are going to go on and do great things … I wouldn’t have left him if he hadn’t had such a tight grip – such a tight grip.”

Asked by Norton why she had decided to write the autobiography now, she said: “I don’t know. There’s no reason for almost anything I do.” Asked what it was like looking back, she says: “It was OK and interesting, but I didn’t feel anything. I remembered it, I wanted to do it, and I did it. Originally, I didn’t want to tell anyone anything, but then I thought I should either tell it or give back the money!”