A "dirty old man" has been jailed for five years and four months for a three-year campaign of internet stalking against two schoolgirls.

Mark Vincent contacted the first girl when she was 13 and during three years of grooming her for sex with him, used sexual blackmail and threats against her loved ones until she was suicidal, York Crown Court heard.

Vincent told her he would give her ailing grandmother a fatal heart attack by sending her a sexual photo of her grandchild, adding: “I’ll dance on her grave”.

Andrew Semple, prosecuting, said when he accidentally sent a picture of his face to the first victim, she realised he was 47 and not the teenager he had masqueraded as, and she went to the police.

By then, he had started stalking her friend, having got her details through Facebook, and threatened to put naked pictures of girls with her face superimposed on the internet. He bombarded both with messages and phone calls.

When officers arrested him in Surrey, he had 70 items of computer equipment and mobile phones, some of which had nude photos and a sexual film of the first girl that he had persuaded her to send him.

Vincent was a "dirty old man" whose actions were designed to get the first girl to have sex with him, the Honorary Recorder of York, Judge Paul Batty QC, said.

“You spun a web of lies to that child. You became utterly obsessed with that child. You were a deeply disturbed man who was intent on getting your way with this girl no matter what.”

Vincent, of Bedfont Lane, Feltham, Middlesex, pleaded guilty to four charges of possessing indecent photos of the first victim, one of distributing an indecent photo by sending it to her, one of harassment of the first girl by putting a person in fear, and one of harassing the second girl. Both live in the Selby area.

In addition he will be on the sex offenders’ register and was made subject to a sexual harm prevention order restricting his use of the internet, and to a restraining order to protect the two girls, all for life. He had no previous convictions.

Detective Constable John Atkinson of York Serious Crime Team praised the girls for speaking out when they were terrified by Vincent's threats. He said: “It was shocking to see laid out in messages, children talking about needing to do homework or attend school clubs only to have Vincent overwhelm them with demands and threats until they gave in to his will.

"I want the victims to feel proud they have managed to bring an end to their abuse, and also ended abuse for many other of Vincent’s victims.

“I also want to encourage anyone who thinks they are being targeted or bullied online to come forward. Come and talk to the police, we take all reports of this type of crime seriously and we will listen to you and support you every step of the way.”

For Vincent, Martin Robertshaw said the threats had been “hot air” which he had never planned to carry out. He had never met the girls or made plans to travel to their home area. The computer equipment related to his job with an auction firm.

"Things as far as he is concerned have hit rock bottom. They cannot get any worse for him," said the barrister. Vincent had lost his partner and his son over his crimes.