Louis Theroux reveals one subject he was 'too scared' to film for documentary

Few things that frighten Louis Theroux, but one definitely does.

His illustrious, 28-year career as a documentarian has brought him face-to-face with serial killers, drug lords, white supremacists and everyone in-between - including one of the UK's most prolific sexual predators, Jimmy Savile, whose heinous crimes hadn't even been exposed when they caught up.

In his latest project, Inside the Manosphere, Theroux met with a group of 'extreme male influencers', infamous on social media for their inflammatory views on masculinity and promotion of content accused of 'radicalising' young men and degrading women.

Despite the controversial beliefs of the characters he met through the feature-length Netflix film, the 55-year-old recently insisted there's only ever been one subject throughout his career that he was 'too scared' to address.

"As far as actual subjects, the one that I kind of wanted to do but didn’t do mainly out of fear was going out to ISIS," Theroux admitted during an appearance in a LADbible 'Honest Box' video on YouTube.

"Remember, the so-called Islamic State, when they were executing people in orange jumpsuits and rounding people up and throwing them off tall buildings, incinerating them, crucifying them."

He'd been approached with the idea of centring a documentary on the terrorist group (otherwise known as Daesh, or ISIL) sometime in the 2010s, but deemed the prospect unsafe for both himself and his team.

Though ISIS' threat has since been deemed slightly less than it was 15 years ago, the group remain attack, having carried out deadly attacks in both Australia and Syria last year.

Theroux confessed he was concerned for his team's safety (AHMAD AL-RUBAYE/AFP via Getty Images)

Despite this, father-of-three Theroux insisted he still has no drive to liaise with members.

"It felt like this weird reanimation of a medieval mindset, like the most extreme, almost pornographic violence being enacted," he continued.

"For me as a student of the human condition and forms of organised madness, it felt like the best example, the most horrific but also the most flagrant example of rampant, also contagious, irrationality, but I genuinely wouldn’t have felt safe going out there, even for me or my team so we never went."

During the same interview, Theroux was asked, Who's the worst person you've met?, which he laughed off as a 'somewhat subjective' question.

"I've been in prisons, I was in a maximum security mental hospital for pedophiles making a documentary," he recalled, going on to admit, however, "My mind tends to go to Jimmy Savile."

The British presenter explained: "Actually, when I met him, I was making a documentary, but his crimes had not been discovered."

Theroux interviewed Savile in 2000 (BBC)

Theroux met the Jim'll Fix It star in 2000 whilst filming When Louis Met... Jimmy, during which the journalist asked Savile about rumours of illicit behaviour with young people.

The 1980s DJ died 11 years later, after which a horde of sexual abuse allegations came to light, many made by children and the elderly.

Savile was posthumously handed over 2000 criminal offence charges by UK police, including both rape and sexual assault.

"So, it was that that strange dissonance of later finding out that he'd done these dreadful things," Theroux recalled of their get-together. "He'd been a serial sex offender, and not knowing at the time.

"But he's well-advertised as probably the worst kind of 'VIP predator' or person in the public eye who was a predator, certainly of recent times."