Image caption Theroux and Savile went on to become friends

Documentary maker Louis Theroux is to revisit one of his subjects, Jimmy Savile, by making a new film about him.

Savile was one of Britain's most prolific sex abusers and is thought to have assaulted hundreds of people between the ages of five and 75.

Theroux made When Louis Met Jimmy in 1999 and 2000, forming a friendship with him until 2004.

Savile died in 2011 but was not unmasked until 2012, by an ITV documentary.

Image caption The second film aims to look at the impact of Savile's crimes

Until then he had been known as an eccentric figure who raised £40m for charity and was famous for tea-time TV favourites like Top of the Pops and Jim'll Fix It as well as stints on BBC Radio 1.

BBC Two's Newsnight had also investigated allegations of sexual abuse by Savile, but the report was shelved, prompting an inquiry by former head of Sky News Nick Pollard in 2012.

The report criticised the BBC's management, but found no evidence of a cover-up.

Theroux's first film set out to ask questions about Savile's private life and allegations about paedophilia but the ex-DJ was careful to reveal as little as possible.

The second film will try to "understand the truth more fully" with interviews with people who Savile knew and introduced to Theroux between 1999 and 2004, and his "victims, friends and family".

It will also explore the impact of Savile's crimes and how his public image afforded him immunity.

Kim Shillinglaw, controller of BBC Two and BBC Four, said: "BBC Two should be part of the national conversation and this challenging subject matter is the kind I want to see on the channel.

"Louis Theroux is one of the country's most talented filmmakers, and I am very pleased that he is revisiting this important - and deeply personal - subject for us, asking difficult questions about the life of Jimmy Savile and those around him and exploring the impact his crimes had on his victims."