A pervert travelled to Kent from Sussex in the belief a father would allow him to sexually abuse his two young daughters, a court heard.
Wayne Booker arrived with a bag of sex toys, condoms and a mask ready to have sex with girls aged 11 and seven.
But the 53-year-old architect, who has done charitable and voluntary work on historic sites with children, soon discovered he had been the victim of a police sting and was promptly arrested.
Pervert Wayne Booker has been jailed for five years
Among videos he distributed to an undercover officer was a four-minute "tutorial" for paedophiles on how to abuse a child.
Booker, of Crabtree Lane, Lancing, West Sussex, was jailed for five years today after admitting 11 offences of distributing indecent photos of children, three of assisting or facilitating the commission of child sex offences, one of arranging facilitation of child pornography, six of possessing indecent photos of a child and three of making indecent photos of a child.
Under an extended sentence he will not be released under he has served two thirds and he will be on licence for a further four years.
Maidstone Crown Court was told the undercover officer made contact with Booker on the internet in November last year and told him he had two daughters.
Bearded and balding Booker described various sex acts he wanted to indulge in with the children. He also sent child sex photos and videos to the officer.
The case was heard at Maidstone Crown Court
Prosecutor David McNeil said a meeting was arranged and when he arrived in Maidstone the child protection team pounced. They seized the bag containing vibrators, love beads, condoms, lube and a mask.
When interviewed, Booker said he asked to have sex with the girls after the officer indicated he was "up for some fun".
He bought the sex toys on eBay for the occasion and said the mask was for "role play" and not for any sadistic intention.
As well as almost 300 images Booker sent to the officer, he had nearly 3,500 on his computer at all levels. Another 1,489 had been deleted.
"I am delighted that someone who was so determined to sexually abuse very young children has been prevented from doing so and brought to justice..." - DS David Shipley
Booker's name will appear on the sex offenders' register indefinitely. A sexual offences prevention order was made and he will be banned from working with children.
Booker sat with his head in his hands as John Fitzgerald, defending, said he was "candid in the extreme" when arrested.
"He has led a blameless and constructive life," he said. "He is an architect who does voluntary work in his community for historic monuments where school classes visit.
"He has never committed offences before, let alone of this gravity. These are life-ruining convictions for him. I cannot overstate the impact they will have on him.
"He was leading an everyday life and was arrested. His life has changed forever. He has been in custody four months. It has had a massive effect on him.
"When told further offending was assessed as high, he looked stunned. He said: 'I am never going to do this again. I am not coming back here.'
"This was brought to his mind by adult pornography. His every move online will now be followed and policed. He will have no unsupervised contact with children under 16."
Mr Fitzgerald added Booker was not in a relationship and had no children.
Judge Michael Carroll said Booker intended to sexually exploit children and represented a significant risk of causing future serious harm.
"You were not only an avid distributor of this filth, but in possession of a large amount, probably for your own gratification," he said.
"You then went beyond that and, to put it bluntly, wanted to put your fantasies clearly into practice.
"I have no doubt in my mind whatsoever that when you set off that day and met up in Maidstone with your contact you believed you were going to abuse children."
DS David Shipley said: "I am delighted that someone who was so determined to sexually abuse very young children has been prevented from doing so and brought to justice.
"From the items Booker had in his possession when he was arrested it was apparent that he had every intention of committing sexual offences against innocent children.
"In the child exploitation investigation team we will use imagination and the full extent of our technical and legal capabilities to protect children in Kent from those who seek to cause harm."