His new series of documentaries is about to drop, but there's still one subject and man that eludes Louis Theroux.
Chatting to Be ahead of the release of his latest series which is set to air onBBC Knowledge from November 21, the 47-year-old said controversial rapper R. Kelly is yet to take him up on the offer to be filmed.
"I have always said I would like to make a documentary about R. Kelly," Louis told Be when asked who his ultimate documentary would be about.
The British presenter added that although he's always been a fan of him as an artist, Louis added he would want to explore the allegations leveled at R. Kelly that he runs a "sex cult" and holds women against their will in his properties.
"I have said that five or six years and that was before it came out the allegations he was running a sex cult, which I’m sure he denies. The invitation remains open," he added.
"I think it would be fascinating to go on the road with R Kelly and just see him in his life. I think he is a tremendous artist and he has a brilliant voice and a terrific composer, but he also seems to have this other side that is problematic and I would be very curious to see what it would be like living in his world."
And while R. Kelly may have denied being the "mastermind" behind a cult, Louis also spoke about his new series, including his documentary Trafficking Sex, and his first-hand experience at seeing how a group of women live and work on the streets of Houston
While some women who are working in the illegal sex industry in the American city opt to have a pimp, others do not, and Louis added it's complicated when trying to work out whether or not they're safer for it.
“I think it’s complicated, you’re talking about these conditions these women are in are apocalyptic almost in their awfulness. The world’s that they’re in, especially those on The Track or The Stroll, where woman illegally work as prostitutes they are lawless frontiers," he said.
"So you’re in a situation that is desperate and dangerous so in that situation you need protection but the pimps, from what I can tell, pretty awful and it’s hard to know how exactly it goes down.
"We get as close as we can but everything that I saw suggested that it was just a horrible and desperate existence and one can only assume that without the pimps in that world, even more horrible and desperate. But what a choice to have to make."
A new season of Louis Theroux begins 21 November at 8.30pm on BBC Knowledge with five diverse film, starting with an exploration of three American cities facing devastating challenges: sex trafficking, murder and opiate dependence.