For the past year, I have been living a dual life. To my friends, I am Patrik, a 25-year-old gay man studying for my master’s in London. To those inside a terrifying and violently race-obsessed world, I have been “Erik”, a dissatisfied Swede who came to London inspired by Brexit and to get away from the liberal bias of Swedish universities.

On behalf of Hope not Hate, as it launches in America, I have spent 13 months infiltrating the upper echelons of the “alt-right”, a movement with strongly antisemitic, conspiracy- and race-obsessed far-right members, which has tentacles across the world, online and off. Its core belief is that “white identity” is under attack and its influence has reached as far as the White House.

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I secretly recorded people who wanted to deport Jews and Muslims and who talked of murdering leftwing opponents, and I even met people who boasted of direct links to the Trump administration. I witnessed the terrible violence in Charlottesville, Virginia, which left a woman dead after a car was driven into anti-racist protesters.

The “alternative right” (which has two wings: the harder-edged “alt-right” and the more culture-obsessed “alt-light”) has received more attention since the election of Trump and, in particular, Charlottesville. But it’s still a largely misunderstood and sometimes underestimated movement.

A common question I get is: “Aren’t they just doing this for fun?” particularly given the strong online and trolling presence. The answer is no. Jokes and irony are an important aspect of the online spheres where the “alternative right” mobilises but it cloaks an effective means of radicalising young people and getting the message out. Behind the irony and trolling are much more sinister ideas.

On a Friday in June, I was invited to a barbecue in a suburb of Seattle. The house was a temple to national socialism. Swastikas covered the walls, a bust of Adolf Hitler perched on a side table and Mein Kampf was on the bookshelf, alongside works by Mussolini and second world war paraphernalia. Most of the people there were men in their early 20s.

“We’re all about the 14 words,” a guy called Kato told me when I arrived, referencing an infamous 14-word white supremacist slogan, “We must secure the existence of our people and a future for white children”.

“Whites are going to be a minority in this country by 2040,” Kato added, before telling me about the impending “race war”.

The mood at the barbecue was light-hearted but I was scared for my life. These men were talking about the coming race war and explained in detail what they wanted to do with anti-fascists and Jews (who, for these people, were essentially the same thing). Holocaust jokes punctuated conversations about their most prized possessions: their firearms. The mix was absurd.

Exposing the inner workings of these groups is important. Using a hidden camera I did just that, as part of Hope not Hate’s wider report into the far right. But I did not spend a year infiltrating far-right groups just to catch extreme racism on camera. There are easier ways to do that – many of their views have already been published online. Certain topics, however, are discussed only behind closed doors.

I had initially managed to infiltrate groups here in Britain, such as the London Forum, which is the UK’s most important far-right thinktank. Luckily for me, Scandinavian heritage and culture is fetishised by some within the UK far right, meaning interest in my Swedish background cancelled out any suspicion. (At formal dinners we sometimes opened by drinking from a ceremonial Viking horn before raising it to the ceiling in a prayer to Odin.)

I got insight into how this movement strategised. I’ve had conversations with individuals from the British far right regarding how they should frame and phrase the “Jewish question” in order to appear as respectable as possible. I recorded a prominent American far-right figure explaining how they were going to “bring the mainstream towards us”, before revealing a plan for Jews to be deported and the abolition of voluntary birth control. Being on the inside allowed us to capture the true face and beliefs of this movement.

Spending a year inside the far-right community numbs you. The extreme views started to feel almost normal many months ago. Few things shock you after spending a year with these people; I became desensitised and started to lose perspective of how absurd their ideology was. Ideas that I once reacted viscerally to I could listen to for hours without raising an eyebrow.

Allowing these hateful ideas to go unchallenged normalises them. It brings about a creeping acceptance: even if you’re fundamentally against these notions you learn to live with them. Indeed, I was told that this is an explicit strategy by some of the leaders of these groups.

And it seems to be working. Just look at Charlottesville, where young people dared to march unmasked next to Nazi flags, unconcerned about any social cost. If we don’t stand up every time we see racism, sexism, homophobia or oppression of any type, we run the risk of it becoming normal.

• Patrik Hermansson grew up in Sweden, where he worked for the far-right monitoring organisation Expo. He is now a researcher for Hope Not Hate. The year he spent undercover in the alt-right is being made into a film called My Year In Kekistan