David Bowie only discovered he had terminal cancer three months before he died, a new documentary reveals.

The superstar died on 10 January last year just a few days before his 69th birthday.

He had just recorded his last album Blackstar, which many described as his parting gift to his fans.

But Johan Renck, who directed Bowie's last music video Lazarus, said his death-shrouded performance was not in fact about the singer's illness.

"To me it had to do with the biblical aspect of it, you know the man who would rise again.

"It had nothing to do with him being ill. I just liked the imagery of it."

Renck said Bowie discovered his cancer was terminal the week they were shooting the video.

"I found out later that that was when he knew it was over.

"We'll end treatment or whatever capacity that means, that his illness has won."

The interview features alongside rare and never-seen-before footage of Bowie in a BBC documentary.

It is released to coincide with what would have been Bowie's 70th birthday on 8 January.