The broadcaster's long-awaited series Forbidden America sees him film some of his toughest scenes yet. Gemma Dunn finds out more.

Louis Theroux is mulling over his bucket-list interviewees.

The 51-year-old documentary-maker, who has spent the best part of 25 years getting under the skin of many famous subjects (as well as studying taboo subcultures), has come up with his top three.

"Tom Cruise. Only because of my history with Scientology..." he begins, pensively. "People are either scared to ask him about it or they feel like it'll create an awkward mood. Whereas I just think someone talking to Tom Cruise about what's really going on inside Scientology would be really valid.

"Then I feel the story that I missed was Isis when it was going on," he lists as second choice. "Quite who I would have interviewed... Anyone in a position of authority there. Or even now, (someone) still signed up to Isis or some radical Islamist or a regretful Jahidi like Shamima Begum.

"And my third one will be, maybe, Lisa Marie Presley," he concludes, without elaborating.

And with a back catalogue like Theroux's - an evolution that spans from sitting down with Jimmy Savile to accosting cult members to making films on eating disorders and dementia - there's little the seasoned interviewer can't handle.

But while he awaits his desired trio, the popular broadcaster has yet another BBC Two series to promote, titled Louis Theroux's Forbidden America.

The new three-parter, which sees Theroux travel the length and breadth of the United States, explores the impact of the internet and social media on some of the most controversial corners of American entertainment.

"The world has gone through massive changes in the last few years, in particular from the effects of social media," he reasons, having originally planned filming for early 2020 before the Covid-19 pandemic hit.

"Far-right groups that have found new influence through gaming and streaming services. Porn performers who have seen power shift to them as they've embraced creator-controlled apps and called out alleged predators in the industry. And in the rap world young men with big dreams caught up in feuds and high-risk behaviour in the click-driven world of social media.

"These documentaries were tough to make," he admits. "They required delicate access conversations. They feature scenes and confrontations that are shocking and upsetting. But they are also powerful depictions of a world that has become strange in ways we could never have imagined 10 years ago."

It's not the first time Theroux has entered these worlds, however.

Who could forget his documentation of the booming Californian porn industry in 1998? Or his rap battle in 2000? Both as part of his infamous Weird Weekends format. Or even Louis and the Nazis, in the early 2000s.

So why revisit them now?

"It wasn't something that I consciously planned," he answers. "I'd made a number of programmes set in the UK that touched on social themes, medical themes, themes of mental health. And I think part of me was missing, well sort of craving, a change of pace, a change of mood.

"As you know, I started out making programmes in America and made my name, in some respects, with Weird Weekends. And there's something about those stories - they have an outlandishness, an eccentricity that felt very different to what I've been doing.

"And so I thought, 'Well, let's go back and do one of those slightly weird American cultural stories'."

In the first film Theroux meets young and highly inflammatory figures from the far right (what he refers to as "the hipster far right") including those who recently came to the broader public's attention through the notorious Capitol Hill riots.

One such name is Nicholas J Fuentes, a 23-year-old far-right, white nationalist political commentator who brands Theroux "pretentious".

Another is Kentucky-based streamer Beardson Beardly, who throws the film-maker out of his house after he questions him over an alleged Nazi salute.

"It's happened to me over my career probably 10 or 15 times; I've been thrown out of an interview, or someone's put their hand over or told me to f*** off, or whatever it is," the bespectacled father-of-three offers.

"To me, as a sensitive person, it never feels that good. I don't enjoy people who are visibly upset. And at the same time, you know, it is what it is, and you recognise that it will make explosive and probably entertaining footage."

He questions: "When I look back, my honest thought was, 'I wonder if I left too quickly?'. If he says 'Leave my property', I guess I have to. But another part of me thought, maybe I should have just said, 'Well, why don't you make me?'"

Another chapter in the series explores the porn industry as it grapples with its own Me Too movement, the rise of platforms like OnlyFans, and how social media has evolved into a space to publish accusations of sexual misconduct.

And Theroux's most personal film ("although I don't play favourites"), is centred on the world of rap and hip-hop in the southern states of America, and in particular Florida. Rappers, like many artists, have long mined their lives for inspiration to create and promote their music. But raising the stakes is the 24-hour connectivity of social media.

"I'm a fan of rap; I see the world of rap as something that I admire, and I try and hold on to that respect for the artistry of the people involved, and the humanity of the people involved," states the Londoner.

"And, actually, I suppose that's the biggest part of the job in a way, building rapport. It doesn't always happen the way you want, but what you find is, if you go in as a sort of sympathetic presence, or at least in a mode of listening and paying attention, that people, for the most part, are happy to open up and feel grateful for you being there," he imparts.

"There's no recipe, there's no formula for making sure that the films do have a degree of compassion and warmth in them, other than really spending the time just being attentive and just being curious."

Does he see his interview style as straddling observational and, at times, confrontational?

"It's always a hybrid, and whatever success I've enjoyed on TV, I think it's been down to the fact that I had a mixture of real respect for actuality and things unfolding on screen in organic ways," Theroux concludes.

"Somehow that mixture of things happening in surprising ways, but also me slightly pushing and asking questions and presenting, made things work.

"But I'm a little more confrontational (now). A tiny bit more. I'm 51, a bit more serious, and I'm trying to take on subjects that I'm curious about.

"I'm an older man; I'm more comfortable at sort of bringing the fight, not literally, hopefully not physically, that would be inappropriate!" he quips. "But being a more robust questioner, if you like."

- Louis Theroux's Forbidden America starts on BBC Two on Sunday, February 13.