Image copyright One Young World Image caption Bjorn Ihler survived an attack and now wants to tackle extremist ideas

Bjorn Ihler read Anders Breivik's book only a week after jumping into the waters of Tyrifjorden in Norway to escape the terrorist's bullets.

Bjorn was one of the survivors on Utoya island where Breivik killed 69 people in July 2011, after killing eight in Oslo earlier the same day.

What Bjorn found in the far-right "manifesto" surprised him.

"His worldview was not purely driven by hatred," he says. "It was much more about fear of what was happening to his society.

"This was a guy who grew up in the same city as me, we had similar backgrounds, we went to similar schools, but he saw the world in a completely different way."

Since this experience, 26-year-old Bjorn devoted his life to trying to keep other young people from following a similar path to Breivik.

Looking for extremists

He has scoured the internet and seeks out extremists and former extremists to understand how they came to their views.

He claims the unusual and unenviable record of meeting more reformed extremists than anyone else.

Image copyright Getty Images Image caption Bjorn wanted to tackle the "mindset" of Anders Breivik

And he is now one of the leaders in a project talking to students in UK schools about extremist ideas.

Bjorn says that before Breivik appeared in court after the attack, people were describing him a "super-intellectual far-right monster".

In an echo of Harry Potter's nemesis Lord Voldemort, some were calling Breivik "He Who Must Be Named".

Image caption In 2012 Bjorn gave evidence of how he had escaped by jumping into the lake

But when Bjorn saw Breivik in the dock, he realised he was no longer at risk from him.

"I decided that the problem to address right now is all the people who share his mindset," he says.

Bjorn is part of an initiative called Extremely Together, a partnership involving the Kofi Annan Foundation, One Young World and the European Commission.

Not shutting down debate

Bjorn's main recommendation for schools is that they teach students that people are allowed to hold very different ideas and opinions.

"I would like to see a class teaching critical thinking or philosophy in every school," he says.

Image caption Extremely Together visit schools with a message of open debate

"Students need to learn to analyse the information they receive, and to understand that there are many ways to interpret information, rather than see the world as black and white."

He is concerned that many education systems are "shutting down critical thinking and teaching propaganda".

Bjorn says teachers should encourage students to share ideas in the classroom, however unpleasant some of the ideas might seem.

He says the mentorship of his old philosophy teacher helped him get through a difficult year following the attack.

"I was all over the place, I couldn't make sense of anything, so I decided to call my old high school philosophy teacher," he says.

"He had taught me that people can see the world in different ways. If Breivik had had him as a teacher, I think things could have been very different."

Against 'safe spaces'

Bjorn says the trend towards safe spaces in educational institutions is "extremely destructive" because it means teachers are hesitant to allow discussion of sensitive subjects.

"I've probably met more former extremists than anyone else, and one thing they all shared was that no one outside of their group would listen to them," he says.

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"They never felt they were valued as human beings, they said no one would listen to their ideas.

"The only way to stop people from believing these ideas is to build a culture in the classroom where they can be discussed, analysed and criticised."

Image copyright Reuters Image caption A memorial after Breivik's deadly attack on Utoya island

He says this feeling of alienation is a "driving force" for why people turn violent. "If they cannot promote their worldview through democratic means, they do it through violence."

Countries around the world have been examining how to counter extremism in educational institutions.

Bjorn warns that too much interference in schools could "backfire" - if students feel they are being unfairly targeted, they will feel targeted and be more prone to radicalisation.

He argues that trying to ban access to extremist material online is "not a solution".

"Educational institutions should be places where you are allowed to have weird ideas and discuss them without being reported to the police or have it show up on your record," he says.

"There is a difference between security and safety, and schools should not be places where ideas and opinions are policed."