The final episode of Louis Theroux's Forbidden America aired on BBC 2 on Sunday night.
In this three-part documentary, Louis Theroux looked at the effect of the internet and social media on some of the most controversial groups in the US, including the far-right, Florida rappers accused of involvement in illegal gang activity and prominent figures in the porn industry who have been accused of predatory behaviour.
Over the years, Theroux has encountered many extreme groups and controversial figures, such as Scientologists, neo-Nazis and, most famously, Jimmy Savile.
While viewers have praised the documentary-maker for his journalistic ability to explore taboo subjects, he has also been criticised for giving airtime to people with offensive and potentially harmful opinions.
Yahoo looks at some of the most controversial moments in Theroux's nearly three-decade-long career.
Louis Theroux's Forbidden America - Extreme and Online
In the first episode of his new series which aired on 13 February, 2022, Theroux met members of the American alt-right who mainly operate on the web but have been influential in real life political events, including the Capitol Hill riots in 2021.
The documentary featured video streamer Anthime Gionet (also known as Baked Alaska), who describes anti-Semitism as a "made-up term", and political commentator Nicholas Fuentes who thinks that America is losing its true identify because of ethnic diversity.
The episode had a largely positive response from viewers, but some expressed concern that Theroux was giving a platform to right-wing extremists.
Mixed feelings about the latest Louis Theroux doc. I'm just not sure his 'give them enough rope' approach is effective against bigotry anymore. These people aren't hiding their views and a documentary gives them a platform to reach more people who might agree.
— David Owen (@davidowenauthor) February 14, 2022
Responding to takes like this in a recent interview with the BBC, Theroux said: "I think the first point would be that these [harmful] voices are already amplified, right?
"I mean, they already have access to hundreds of thousands, if not millions, of tender young ears, eyes and minds by dint of the internet."
He added: "By not reporting on it, it's not going to go away."
When Louis Met Jimmy
Theroux has spoken about the controversy surrounding his interview with sexual predator Jimmy Savile several times.
The broadcaster met Savile in the infamous episode When Louis Met Jimmy which came out in 2000, before historic allegations of indecent assault became widespread after Savile's death in 2011.
When asked whether he had any regrets about featuring Savile on Loose Women, Theroux said: "It was a very complicated set of emotions that lasted for months and, in fact, years."
He said that he "hadn't ruled out" that Savile was a predator while filming the episode, but he concluded that there was "a part of him that I still hadn't figured out".
When hundreds of allegations against him surfaced a decade after the interview took place, Theroux said that he felt "a mixture of complete shock and then also a feeling of 'so that's what it was - that's what he was hiding'".
The Most Hated Family in America
Theroux first visited the Westboro Baptist Church back in 2007.
The highly-inflammatory Kansas church is led by the Phelps family, who are also known as the most hated family in the United States because of their deeply offensive opinions.
Their controversies include picketing the funerals of US soldiers killed in service, staging anti-homosexuality and anti-abortion protests, and directing hate towards people of Jewish backgrounds.
When asked about the potential dangers of humanising people with bigoted opinions in an interview with SBS, Theroux said: "One of the things that made me okay about documenting them and giving airtime to their views was that it would be self-evident that the views were totally idiotic."
He added: "That isn't to say that one out of a million [people] might see it and think 'hey that makes perfect sense.
"But, you can't really let your programme and decisions be guided by the fact that there's some psychotic people out there."
America's Most Dangerous Pets
Before Netflix's Tiger King took over social media in April 2020, Theroux interviewed Joe Exotic during his documentary on America's Most Dangerous Pets in 2011.
Former zoo-owner and TV personality Joe Exotic is currently in prison for his involvement in a murder plot against animal welfare activist Carole Baskin, as well as 17 charges of animal abuse.
Speaking about the mass media attention that Exotic has received, Theroux told PA: “It’s an extraordinary situation Joe is in now. He’s one of the most famous people in the world, arguably.
“But it’s a mixed blessing because there’s a tendency to see them as fictional characters … whereas they are real people involved in a real crime."
In 2021, Theroux released a documentary called Shooting Joe Exotic, in which he met with old friends and family members of the 'Tiger King', in order to present a story which was "close to the truth and a bit less caricature-ish" than the Netflix series.
A Place for Paedophiles
In 2009, Theroux interviewed patients at Coalinga State Hospital, a hospital which houses over 500 convicted paedophiles who have been deemed too dangerous to be released.
The show sparked viewer complaints as some thought that Theroux was being too easy on the convicts considering the crimes they had committed.
Theroux has admitted that during the filming he wrestled with whether he could ever allow himself to believe these people could be rehabilitated.
In an interview with Vice, he said it was "quite a big change" from his previous topics.
"There were little bits of humour there, but not much," he said.
However, Theroux insisted the purpose of the documentary was to look at the challenges of living with these convictions and to discuss what solutions may be available to stop child abuse from taking place.
Louis and the Nazis
Back in 2003, Theroux travelled to California to meet Tom Metzger, a man once dubbed "the most dangerous racist in America" and a US white-nationalist duo called 'Prussian Blue'.
The programme attracted controversy because some viewers saw it as popularising neo-Nazi hate and viewers were particularly uncomfortable with the inclusion of the musical duo Prussian Blue, a pair of 11-year-old sisters who were encouraged to sing far-right nationalist songs by their mother.
In an interview with Metro, Theroux said: "Back in the days of when I made Louis and the Nazis, I spent days, if not a couple of weeks, with basically card-carrying national socialists – people who had the most extreme version of Nazism as you can imagine.
"I think the reason I felt it was OK was that it was so far outside the window of acceptable discourse that it was verging on pathology. If they had been closer to the mainstream you might have imagined we are giving them some sort of currency."
My Scientology Movie
In 2015's My Scientology Movie, Theroux tried to reveal the inner workings of the hidden organisation which has links to a number of Hollywood celebrities, including Tom Cruise, John Travolta and former member Leah Remini.
After being denied entry into the church's official headquarters in 2015, Theroux created a reconstruction of what life's like inside the church with the help of former senior Scientologist Mark Rathburn and a team of actors, as well as real footage of the church trying to stop the film being made.
It addressed accusations of bullying made against the church by former members and its aggressive tactics for dealing with critics.
When asked about the experience by Australian broadcaster SBS in 2019, Theroux said that is was the most unusual moment of his career.
"There were moments when I thought I was going to start losing my temper which is quite an uncharacteristic feeling for me in my work mode," he said.
The Church of Scientology responded by denouncing the film as factually incorrect, while Theroux claims that he was stalked by members of the organisation who disagreed with what was shown.
Louis Theroux: Forbidden America is streaming on BBC iPlayer.
Watch: Louis Theroux discusses My Scientology Movie