A Dover teenager who groomed young girls over the internet and filmed them undressing for him has been jailed for 12 years.

Evan Prevett, 18, befriended the girls aged 12-17 in Canada, Texas and Scotland.

He used social media such as Skype, Snapchat, KIK and AskFM to form friendships with them and then viewed them undressing for him, making recordings on his phone and computer.

The mother of one of the victims travelled 850 miles to see him sentenced by Judge Adele Williams on Friday.

She told the court: “I feel I have failed in keeping my daughter safe. We have found out that our daughter received disgusting and depraved messages. She is now 14 but was 12 when contact was first made and she was a loving, caring and outgoing girl.

“Now she has low self esteem and has lost confidence. She bottles things up and suffers from depression and anxiety. She is quiet and withdrawn and unable to sleep. Her school work has suffered and she has found it hard to go to school and has panic attacks.

“As parents we feel devastated that she has been robbed of her childhood.”

Anthony Prosser, prosecuting, told Canterbury Crown Court that Prevett began threatening the girls that if they did not perform other sexual acts for him to watch he would send the images he had made to their parents, schools and friends.

“The crown says he was simply blackmailing them into performing sexual acts for him for his own gratification,” Mr Prosser said.

Prevett, of Folkestone Road, admitted blackmail, taking indecent images of a child and inciting child pornography just before his trial was due to start in April.

Mr Prosser said Prevett, who was 17 at the time of the offences, carried on with his activities after he was arrested.

Judge Williams told him: “You gained these girls’ trust and made them believe you were their friend or boyfriend. You have caused enormous harm by your crimes.

"You sent them deeply unpleasant and threatening messages and on occasion a deeply disturbing sadistic image of a young girl with her throat cut.

“It is impossible to quantify the harm done by this behaviour.

"The sheer fear, distress, humiliation and pressure they felt is well documented in the victim personal statements which I have read and heard.”

Judge Williams said one of the victims had suffered from mental health problems and depression and has had to have treatment.

“You made them all feel very frightened and you robbed them of their innocence and sense of security, confidence and well being,” Judge Williams said.

“You gained these girls’ trust and made them believe you were their friend or boyfriend. You have caused enormous harm by your crimes" - Judge Adele Williams

Paul Hogben, defending, said they were terrible offences and had caused a lot of harm. He said Prevett had suffered from asthma and had been treated with steroids which had made him put on weight.

“He was bullied at school and at work and the offences he has admitted are bullying offences,” Mr Hogben said.

“His self esteem is very low and he felt he could never form a relationship with a young lady and so he went to the internet and reached out to form friendships he felt he could not form in reality.

“He believed he was forming a genuine relationship and bond which became sexual over time. He now understands what he did and that it was very wrong.”

In addition to the jail sentence Prevett was given an indefinite sexual harm prevention order and will have to sign on indefinitely to the sexual harm prevention register.

Judge Williams commended the courage of the victims and commended the officer in the case.