A man who was sexually assaulted by a children’s television presenter has spoken of how climbing and mountaineering saved his life and “sanity” during the 50 years in which he kept the abuse secret.

Iain Peters, 77, who has waived his right to anonymity, was between nine and 13 years old when he was abused weekly by John Earle, when he was a geography teacher and deputy head at a now-closed boarding school in Okehampton, Devon.

The school closed shortly after and Earle went on to present children’s television programmes including Treasure House and Tom Tom, and was a storyteller for the flagship BBC series Jackanory.

Peters broke his silence in 2015 and after reporting the abuse to police, Earle at the aged of 87 admitted six counts of indecently assaulting a boy and was jailed in 2017 for four years.

The former tree surgeon turned commercial writer, who lives on the North Devon coast, wrote a memoir, The Corridor, about how his lifetime of climbing and adventure helped him manage the trauma he had endured since childhood. In November, the book won the prestigious Boardman Tasker award for mountain literature.

“In effect, for 50-odd years I was suffering from PTSD,” he said. “Climbing on the one hand, it can be a very dangerous activity. And in my case, I pushed the envelope of survival in climbing to its limits in many ways. In my younger days I was doing loads of crazy stuff.

Iain Peters: ‘In some ways, climbing, it saved my life. It saved my sanity.’ Photograph: Jim Wileman/The Guardian

“It was almost in response to what had happened to me in terms of abuse and all these other things. In some ways, climbing, it saved my life. It saved my sanity.”

Peters said his favourite outdoor pursuit, introduced to him at the age of three by his grandfather, has taken him all over the world, from the Alps to the Himalayas and Cordillera Darwin on Tierra del Fuego on the border of Chile and Argentina.

“It has enabled me to reach the grand old age that I’ve reached – living the life that I do, and I’m still a climber, even in my late 70s,” he said. “From a therapeutic point of view, it’s helped. It’s helped me considerably, in terms of both of living with abuse, living with the aftermath of abuse … It became my survival technique.”

Peters said he believed climbing allowed him to “disassociate”.

“When you’re concentrating on staying alive halfway up a vertical rock face you can’t then think ‘Oh God, poor me, I was assaulted when I was nine years old,’” he said.

The father and grandfather said the trauma still had a great impact on his life choices, including on relationships as well as his career. He turned down a scholarship at Cambridge and at one stage found himself working in a strip club for the notorious Kray twins.

“The problem with sexual abuse is it’s all about power and the power of the rapist is huge psychologically and physically,” he said. “I was always frightened. I can see this now but I always rejected success because success led to power, and power led to being like a rapist.”

Eventually, he did marry with his first marriage lasting 28 years before he lost his wife to cancer. Six years ago, he married again to Ellen.

He had never shared his experience with anyone before he reported it in 2015 by handing “a grubby piece of paper” recounting his abuse over the counter at a police station in Exeter.

He had previously denied anything had happened to him when reports of abuse at the school – Upcott House preparatory school – emerged in the media.

Asked what he thought would have happened to him without climbing in his life, he shared the experience of his best friend, who was also abused by Earle, often in front of each other.

“He never recovered,” he said. “He didn’t have climbing. He didn’t climb. He lost his mind. He tried to kill me at one stage. He tried to stab me. I said ‘Why?’ He said ‘Because you survived.’”

‘When you’re concentrating on staying alive halfway up a vertical rock face you can’t then think ‘Oh God, poor me, I was assaulted when I was nine years old.’ Photograph: Jim Wileman/The Guardian

“I have had things like climbing, I have had, eventually the ability to have children, to have a successful relationship, all these things have come. And now finally, you know, I’m an award-winning writer, yes, and so many victims don’t have that opportunity.”

Looking ahead, Peters hopes he and his book can be a beacon for survivors of sexual abuse to know they can come forward with confidence.

“We have to create a social culture that will make people feel that they shouldn’t have shame, they shouldn’t have guilt, that they can go for help and more people, particularly young people, should have that opportunity.”