The 60-year-old, of no fixed address but formerly of Whalley Old Road, Blackburn, was jailed for 18 months in November last year.
Arthur Gibson, prosecuting, said: “As part of the development of investigatory techniques in relation to the production and distribution of indecent images of children, the police are now able to subject recovered images to a programme, which is capable of revealing a GPS location, and date and time when a particular image was created.”
The innovative software identified that images had been sent from GPS locations in Liverpool, including Stanley Dock and Kendrick’s nearby home.
Merseyside Police examined his Facebook account, which led them to contact a couple, whose child they believed had been abused and pictured.
They visited the pair, who confirmed it was their child and said they recognised Kendrick’s bathroom in one picture, which led to his house being raided.
Kendrick arrived home mid-search and claimed: “I may have took one or two photos when he was in a nappy, but I didn’t know it was wrong.
“I know my computer was hacked and I had to wipe it clean.”
Mr Gibson said: “The relevance of the nappy is that Howard and the defendant share an interest in a nappy fetish, and a large number of the indecent images involved children in nappies.”
They recovered 3,416 indecent images, including 668 Category A pictures – the most serious category – from Kendrick’s computer.
Mr Gibson said Kendrick, who also had revolting extreme porn, must have distributed the pictures of the boy directly or indirectly to Howard via a third party of sharing site.
The court heard his five other victims were aged between six and 12 when Kendrick, then aged between 10 and 21, abused them in the 1990s and 2000s.
One boy recalled how Kendrick had once been violent, dragged him around and thrown him against a bed, before raping him.
A girl said he pushed her onto a bed, held her arms and covered her mouth when molesting her, hit and threatened her, and repeatedly attempted to rape her.
Mr Gibson said: “On occasions the defendant’s nappy fetish came to the fore – he would make her wear a nappy and walk around the room.”
A second girl told police he asked her to play the game of “being the baby”, made her lie on a bed, undressed and abused her.
Kendrick molested a third girl while another boy was present, making the boy face the wall, before he abused the boy while she faced the wall.
He admitted 16 sexual offences including rape, attempted rape, sexual assault, indecent assault, and making and distributing indecent photos of children.
Victims and their supporters sitting in the public gallery cried as the abuse was described, with one upset man leaving the courtroom.
Some observers snorted in derision when it was said Kendrick – sitting stone-faced and staring straight ahead – claimed to be sorry.
Judge Warnock said Kendrick’s “sexual abuse and degradation” of his victims represented “a disgraceful catalogue of sexual offending”.
He said: “You sexually abused your victims and downloaded indecent images entirely for your own selfish and sexual enjoyment.
“You did not have any consideration whatsoever for the welfare or innocence of these children.
“It seems that you regarded them as objects available to satiate your own fetishes and perversions.”
A psychologist found Kendrick – who claimed he too was a victim of sexual abuse – was “unwilling and unable” to address what he had done.
The doctor concluded he was “an active participant in a sexual fetish”, while a probation officer found he had “little or no insight” into his crimes.
Judge Warnock said: “I am unsure as to the genuineness of the remorse expressed.”
He said Kendrick was a high risk of sexual harm to children and a “dangerous offender”, who must sign on the Sex Offenders Register for life.
This type of extended sentence means the paedophile will spend at least two thirds of the custodial term – 12 years – behind bars.
He will only be freed before the end of the 18 years if a parole board decides it is safe and will be on licence until he is 56.