A prolific paedophile who groomed vulnerable teenage boys online with an accomplice before filming their sexual abuse is HIV positive, it has been revealed.
Anthony Marsh, 53, was one of two prolific paedophiles who groomed vulnerable teenage boys on the internet before filming their sexual abuse have committed "vile, horrendous offences", according to police who investigated the pair.
Marsh, 53, along with Lee Davis, 39, used social networks such as Facebook and Bebo, as well as specialist gay websites, to befriend boys, South Yorkshire Police said.
And officers fear there may be more victims who have not yet come forward.
After grooming the boys online, salesman Marsh and unemployed Davis would meet their victims and sexually abuse them.
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South Yorkshire Police said Davis filmed teenagers at his home or in his van.
And officers believe some of the footage shot by Marsh has been distributed by him over the web.
The pair admitted a string of sex offences at Sheffield Crown Court last month. Today, prosecutors decided they will not proceed with a small number of additional allegations denied by the pair and Marsh and Davis will now be sentenced in December.
Following their convictions, detectives are now keen to trace any more of their victims.
Detective Inspector Delphine Waring said Marsh, of Menson Drive, Hatfield, near Doncaster, and Davis,of Rowena Road, Conisbrough, near Doncaster, were both family men whose wives and children were unaware of what they were doing.
She said they spent hours online grooming their victims.
"Both were family men, both leading double lives," the detective said.
"As well as all the victims of these appalling crimes, the families of both of these men are victims as well.
"Their families have been completely betrayed by the horrendous activity that both of these men have been undergoing.
"Their crimes are absolutely despicable. They've preyed on vulnerable young boys who have every right, in this day and age, to be able to experiment and use the internet.
"And especially young boys who are perhaps confused about their sexuality, it should be perhaps a safe environment for them to be able to experiment and explore online.
"However, both of these men - obviously vastly older than all of the child victims - have gained their trust, have preyed on that vulnerability and groomed them entirely for the purpose of sexual exploitation and sexual abuse.
"And they've actually gone on to meet the young boys in whatever setting that may have been and committed vile, horrendous offences against them."
Waring said: "This abuse has been continuing for a long time.
"They've been contacting people online, either on gay websites of social networking sites such as Facebook, Bebo or BBM messaging, things like that.
"They've been grooming the boys, speaking to them online and then continuing that communication until face-to-face meetings have taken place."
The detective said there was no evidence Marsh and Davis knew each other before they met online.
But, she said, they began to work together pooling information on potential victims.
Waring said she was confident that the pair were not acting as part of a larger paedophile ring.
"They clearly have spent an extraordinarily large amount of time every day online, grooming and gaining the trust of these young boys - a lot of whom were very young, they were confused about their sexuality," she said
The detective said the pair were caught after Marsh was arrested in May 2012 at a hotel in Scarborough, North Yorkshire, when he was spotted with indecent images of children.
The earliest offence the investigators have discovered so far dates back to 2005 and the victims were aged between 13 and 17.
Now South Yorkshire Police believe there could be other young men out there who are victims of Marsh and Davis and in need of help and support.
Waring said: "That's definitely a possibility, unfortunately, purely because of the amount of time these men have been offending against young boys and because they have spent such an extraordinarily large amount of time online, grooming young boys.
"I've obviously made every effort to prioritise identifying any possible child victims but because of the scale of the offending, clearly there will be some young boys out there that unfortunately we haven't as yet been able to identify. If there are any young boys who have been offended against by these two I would urge them to come forward."
Waring said many of the pair's victims were from South Yorkshire, although the others were from across the north of England and the Midlands.
She said Davis and Marsh used pseudonyms but did not pose as teenagers.
The pair appeared before a judge at Sheffield Crown Court on September 27 and admitted conspiracy to commit sexual activity with children, meeting a child following sexual grooming and a number of other sex offences - 55 charges in all.
Marsh, who also used the names Tony Taylor and Tony Smith, admitted sexual activity with a child and possessing and distributing indecent images of children.
Davis, who also used the name James Parkin, admitted raping a 13-year-old boy, sexual activity with a child and taking indecent photographs of a child.
The charges they admitted involved a total of 10 victims - four of whom were abused by both defendants. But officers say there are other victims they know about.
The conspiracy charge admitted by both men involves the contacting of young men to facilitate meetings for sexual offences between May 2004 and June this year.
Marsh and Davis are both in custody and will be sentenced on December 2.