At least 500 victims as young as two were abused by the shamed television presenter Jimmy Savile during his reign as one of the country's most prolific sex offenders, new research shows.
A study by the NSPCC, commissioned for BBC Panorama, reveals confidential documents examining the extent of Savile's offending and his unprecedented access to Broadmoor hospital, where some of his abuse took place.
The report said the scale of Savile's offending inside Broadmoor is higher than previously thought, with Thames Valley Police having received 16 reports of abuse by him inside the special hospital.
It also describes how some awe-struck civil servants erroneously referred to the Top Of The Pops presenter as "doctor", unaware of the trauma he was inflicting on some youngsters behind hospital doors.
The figures show the most common age group for Savile's victims was 13 to 15 - and the youngest alleged victim was just two years old.
Peter Watt, the NSPCC's director of child protection, said: "There's no doubt that Savile is one of the most, if not the most, prolific sex offender that we at the NSPCC have ever come across.
"What you have is somebody who at his most prolific lost no opportunity to identify vulnerable victims and abuse them."
The joint BBC investigation between Panorama and The World At One, which airs today on BBC One and BBC Radio 4, asks how the DJ got so close to the heart of Britain's establishment and why in 1972 the BBC failed to take effective action that might have saved young people from abuse.
In 1988, health minister Edwina Currie appointed Savile to head a task force to address tensions between Broadmoor's management and unions. A confidential Department of Health memo obtained by Panorama suggests that his appointment was being pushed by a senior civil servant.
The documents suggest civil servants were impressed by the entertainer, who died in October 2011. They refer to him as "doctor" Savile and say he wanted to "ease out" staff at the hospital.
They say he went through each of the main departments at the hospital like a "dose of salts".
Savile first became involved with Broadmoor through the League Of Friends charity in the late 1960s. He was later given his own set of keys and a house in the grounds.
Trevor Smith, a former Broadmoor manager and former branch chair of the Prison Officers' Association, said he remembered seeing Savile at a hospital charity day, exchanging kisses for autographs from young girls.
He told the programme: "He (Savile) kissed these girls who was about 13 smack bang on the lips, held his hand behind their neck to pull them forward and he virtually was giving them French kisses."
One of Savile's alleged victims said she was targeted by the veteran entertainer at a BBC talent audition as a 14-year-old in 1971.
She said: " He reassured me by putting his arm on my shoulder and rubbing my arm, and then he gave me a cuddle and so he was touching my breasts, and he kissed me and he tried to put his tongue in my mouth."
She said she was later groomed over a two-year period by Savile in his Top Of The Pops dressing room at the BBC. Asked why she continually returned, she said: "Every time he did a bad thing he would do a good thing...you know, I promise I'm going to get you an agent and they're going to get you paying gigs."
In the early 1970s a newspaper report into an alleged sex scandal at the BBC prompted an internal inquiry by Sir Brian Neill. His report suggested there should be clear guidance about which BBC staff should be responsible for the behaviour and control of young audiences coming to see Top Of The Pops.
But Panorama and The World At One have seen a memo written in August 1972 by the BBC's controller of television administration, which suggests that the advice was not acted on.
The publication of the BBC's review into how Savile carried out a campaign of abuse over decades has been delayed until later in the year.
It has been reported that the Dame Janet Smith review is expected to uncover hundreds of victims and reveal a culture of ignorance which ''protected'' Savile.
A BBC spokesman said: "The BBC has said it is appalled at Jimmy Saville's crimes.
"We're unable to give a commentary on statements in these specific documents as they are over 40 years old, but the Dame Janet Smith review is considering the culture and practices of the BBC during this period and has had our full cooperation.
"We will await their full report."
A Department of Health spokesman said: "Investigations into Jimmy Savile's activities at 33 hospitals, including the joint West London Mental Health Trust and DH investigation into Broadmoor, are ongoing. We expect these reports to be published shortly.
"It is essential that all the information is considered and investigations are thorough in order to learn the lessons about Jimmy Savile's activities."
Savile: The Abuse Of Power is due to air on BBC1 from 8.30pm tonight.