Christopher Reeve's son is "proud" of his mother Gae Exton for opening up about her late ex in a poignant new documentary about the actor's tragic life

He said about how she needed convinced to appear in the project about the star - who died aged 52 in 2004 from heart failure years after being left paralysed by a horse riding accident: "Once we decided we were going to get to this, other family members came on board.

"I mean, once we kind of said we were going to commit to this, we were going to tell the stories we hadn't told.

"We were going to share the memories we never shared before on camera. My mom is incredibly brave to tell her side of the story and I'm proud of her.

Christopher was left in a wheelchair and on a ventilator after his 11995 riding accident, and along with Matthew had daughter Alexandra with British modelling agent Gae.

After they split, the actor married actress and singer Dana Reeve and they had his youngest son Will Reeve, now 32, before Dana was killed by lung cancer in 2006 aged 44.

Matthew added about how she captured home footage used in the new film about his father: "Dana was really the family documentarian, she always had the camera out, she would film things really like, especially if dad couldn't be there so that he'd be able to watch, but she always used it.

"We're very lucky that we had video cameras growing up."

Matthew's sister Alexandra, 40, said she felt her mother's decision to open up in the documentary was "powerful".

She said: "My dad was a young actor who nobody knew to suddenly being on this rocket ship to fame, and she had a front row seat for all of that.

"So it was beautiful to hear her tell that story, and then tell us her love story of her own relationship.

"And then the continued the love story, even after they separated, about how our family still remains really close, because they gave us this gift of having the united set of parents, even after they separated.

"So I'm so glad that was celebrated."

'Super/Man: The Christopher Reeve Story' by directors Ian Bonhôte and Peter Ettedgui is in cinemas from 21 September.