The singer and artist was left reeling when The Beatles icon was shot dead outside their New York apartment block in 1980, aged 40, and Sean has told how his mother is still haunted by her past with the musician.

He told BBC Radio Music 6 ahead of the 44th anniversary of the former Beatle's death on Sunday that Yoko mentioned John "every day" after he was shot and killed.

He said: "I grew up with my mom speaking about my dad every day. She famously cut her hair when my dad died (because) in Japan, you used to cut your hair when your husband dies.

"So she spoke of him every day, and I think she never has moved on from that relationship."

Sean also opened up about John's infamous Lost Weekend - a nickname for the 18-month separation between his parents during which the Imagine songwriter lived with the couple's assistant, May Pang.

Sean said: "The truth is, even when they were apart, they were always talking. So, I don't think they ever really broke up. All his stuff was still in the apartment with my mom. It's not like they had a real separation.

"... It's clear what his view of my mom was in his life. She was monumental, obviously, and the whole album (Mind Games) is about her.

"She's there in the studio … it sort of confirmed how deeply in love he was with my mom.

"... Every relationship is very difficult, and I don't believe that human beings have really solved the love equation.

"So I think they did the best of anyone I can see."