Sir David Attenborough has revealed he had a scrape with death during a rock climbing accident in his youth.
The 89-year-old naturalist and broadcaster, who was an enthusiastic climber in the years before his marriage at the age of 23, said he thought about his parents as he fell "about 30 or 40ft".
He told Susanna Reid and Piers Morgan on Good Morning Britain: " I used to be a mad rock climber - I mean, an obsessive rock climber. And I fell off in the Lake District... And I was absolutely sure I was going to die.
"I thought how ungrateful I was, and what my parents would think. They spent all this time looking after me, and being nice to me and so on, and that was what their reward was. That's what I thought. I felt desperately sorry that I had let my parents down."
But Sir David "gave it up" when he got married to Jane Elizabeth Ebsworth Oriel in 1950.
Pressed by Morgan on whether he would ever retire, the broadcaster said he would keep going " until I fail to do what I do".
He added: "Something's got to go. I don't know what it is. I've got new knees now, which means that I can go faster than I used to five years ago, and that's a huge gift."