Red Saunders, 23, prepared scripts, bought costumes, including an Avatar outfit and edited the films professionally.
He used his charm to trick the parents of two girls aged six and eight to allow him to spend hours alone with the youngsters playing “games”. The predatory paedophile was able to get access to children despite being placed on the sex offenders’ register in 2005.
Saunders, of Redhill, Surrey, was told he would have to serve a minimum of eight years for raping the eight-year-old.
The Old Bailey judge who gave him concurrent sentences for other offences involving children said Saunders was so dangerous, he may never be freed.
A disturbing diary found at his home showed he may have been planning to abduct a girl and kill her.
Saunders pleaded guilty to 24 charges including raping the eight-year-old, sexual assault, inciting children to engage in sexual activity and making and possessing indecent images of children.
These consisted of more than 4,000 videos and pictures he took of young girls.
Judge Peter Rook told Saunders: “You are obsessed with young girls. You have acted out your sexual fantasies.
“Your conduct amounts to every parent’s nightmare.”
The court was cleared of the public while the judge watched a compilation of images made by Saunders.
Saunders advertised online as a babysitter and abused the two girls after answering adverts placed by their parents on Gumtree.
He provided false references and said his criminal records checks would follow.
After spending three to four days with each girl, he left after being able to carry out his abuse and recording it with three cameras.
Edward Lucas, prosecuting, said: “He came over to both sets of parents as plausible, charming and he clearly interacted cheerfully and well with both children.
“He employed his charm and guile in order to obtain one-to-one contact with both these little girls.”
Mr Lucas said the two victims did not understand what had happened but their parents were “distraught”.
He said the eight-year-old complained to her parents and police found images of him abusing the seven-year-old when they raided his home in April.
They also found he had been filming girls in parks and other public areas and editing them with child porn.
A note attached to them asked for the films to be destroyed if anything happened to him. One said: “This is what I live and breathe for.”
Saunders kept receipts and details about babysitting and the amounts he was paid, said Mr Lucas. There was also an “Abduction Diary” setting out in “distressing detail” how to abduct little girls, abuse them and then kill them and dispose of their bodies.
He had made inquiries about chloroform and made reference to a school. The diary ends with the words: “Now it’s time to find the unfortunate little girl.”
Saunders was convicted of sexual assault at Guildford Crown Court in October 2005, after photographing a five-year-old girl he abused at a gym where he was working as a party organiser.
He was given a supervision order involving sessions with a psychologist, and placed on the sex offenders’ register for five years.
Surrey social services reported that he had a “depraved interest” and wanted to fulfil his fantasies, including abducting a seven-year-old girl.
George Payne, for Saunders, said: “The sad reality of this case is that process aimed at rehabilitation failed.”