Louis Theroux feels "confused" about finding Jimmy Savile to be "quite likeable" for a couple of years after making a documentary about him.
The 48-year-old TV star spent three months with the disgraced broadcaster in 2000, when he filmed "When Louis Met Jimmy", which aired years before Savile was exposed as a paedophile.
Speaking to BBC Radio 4's "Desert Island Discs", Louis - who even stayed at Savile's house after shooting the documentary - explained: "There's a slightly naive view that if abuse happens you recognise it as abuse straight away, and of course that isn't how it works in a real world setting.
"So, it was something that I had to learn and I'd like to think that I bring that understanding now to my work and also as a human being.
"I'd remained in contact with him a little bit after I'd made the first programme.
"So, while I'm still quite proud of the first programme, I'm still a bit confused about how was I able to experience him as a somewhat likeable person in the year or two after making it.
"That's something I think upon."
Louis filmed a follow-up documentary about Savile after he was exposed as a paedophile and after his death.
Reflecting on that experience, he said: "I suppose I felt I wanted to figure out how it was that I'd missed what I'd missed.
"I wanted to do a personal and professional stock-taking and to sit down with victims and talk to them about their experiences.
"(There is) something very conflicting about reading about crimes and predatory activity while also knowing that this was someone who you, sort of, quite liked, and trying to square that in your own mind.
"And sometimes ... victims of serious sexual assault experience a similar ambivalence."