A rape survivor has joined forces with her rapist to speak about their experience - and how they have both come to terms with what happened.

In an extraordinarily brave and open TED talk, they both took to the stage to describe how they have come to terms with it - she with how to accept she was not at fault and move on; he with his shame at realising he was capable of behaving that way.

Thordis Elva told the talk that their experience - meeting, sharing and forgiving 20 years after her then-boyfriend attacked her - was not a "formula" for others in similar situations, but said she hoped that by speaking out she could help.

"Nobody has the right to tell anyone else how to handle their deepest pain or their greatest error," she said.

"Breaking your silence is never easy, and depending on where you are in the world, it can even be deadly to speak out about rape.

"I realise that even the most traumatic event of my life is still a testament to my privilege, because I can talk about it without getting ostracized, or even killed. But with that privilege of having a voice comes the responsibility of using it.

"That's the least I owe my fellow survivors who can't."

Thordis, from Iceland, was just 16 when Australian exchange student Tom Stranger, then 18, visited Reykjavik.

They shared what Tom described as a "lovely teenage romance", holding hands at lunchtimes and meeting one another's friends.

It was a month into their budding relationship when they attended their school's annual Christmas Ball together - and, high on first love and "newfound maturity", Thordis tried drinking rum for the first time.

It went badly, and she ended up vomiting and unconscious.

"The security guards wanted to call me an ambulance, but Tom acted as my knight in shining armor, and told them he'd take me home," she said.

But when they got there - she now awake but still weak - he proceeded to undress her and lie on top of her.

They broke up just two days later.

She said for years, she believed she was to blame - for her skirt being too short, her smile too inviting, her drinking too much.

For his part, Tom said he had buried the memory - trying to convince himself it was sex, not rape.

"It is important to now state that I didn't see my deed for what it was," he said.

"It wasn't so much a conscious refusal, it was more like any acknowledgment of reality was forbidden.

"Deep down, I knew I'd done something immeasurably wrong. But without planning it, I sunk the memories deep, and then I tied a rock to them."

He said he had battled to build an image of himself as a 'good person' - a surfer, a loving brother and son, a youth worker.

It was nine years later, when Thordis was teetering on the edge of a nervous breakdown, that she penned a letter directly to Tom, describing everything she had gone through since.

His response, she said, was unexpected - a confession "full of disarming regret."

That opened a door of communication which lasted another eight years, before they agreed to meet in person - choosing South Africa as the middle ground between their two countries.

"From what I've now learnt, my actions that night in 1996 were a self-centered taking," Tom told the talk.

"I felt deserving of Thordis's body. I've had primarily positive social influences and examples of equitable behavior around me.

"But on that occasion, I chose to draw upon the negative ones. The ones that see women as having less intrinsic worth, and of men having some unspoken and symbolic claim to their bodies.

"These influences I speak of are external to me, though. And it was only me in that room making choices, nobody else."

The pair have now written a book together, South of Forgiveness, which discusses their experiences in-depth.

They said they hope it will help others come to terms with the issue of sexual violence in a "new, honest" way - and hope that men will play a bigger role in addressing the problem than they have done to date.

"Despite our difficulties, this journey did result in a victorious feeling that light had triumphed over darkness, that something constructive could be built out of the ruins," Thordis added.

Warning: Some may find the details discussed in this video distressing