A 16-year-old boy blackmailed a classmate into performing a sex act on him after tricking him into sending him a picture of his genitals.

He told his victim he would make the picture public among school friends unless he agreed to do as he said.

And after the victim went along with the demands the teenager, who cannot be named for legal reasons, failed to destroy the image.

He also said he would turn the victim's circle of friends against him unless he did as he instructed.

But when he demanded the lad have full sex with him or risk exposure he went to speak to support workers at school and the police were called in.

Tessa Hingston, prosecuting, told Swindon Crown Court that the boys were in year 11 at a school together.

"Things began to go wrong in February this year when the victim said the defendant started asking him to be more than friends and sent him two pictures of his, the defendant's, penis," she said.

"These pictures were sent by Snapchat, that meant that they are instant, they appear and then disappear: they are not saved or preserved."

She said the lad told the victim that he was worried his penis was not normal and insisted the victim sent him a picture of his so he could compare them.

Miss Hingston said the victim was very reluctant but, under great pressure, did as he was asked believing the transient nature of Snapchat meant they would disappear.

But unknown to him the defendant made a screen grab of the image and saved it to his laptop use to put pressure on the sender.

"He said unless you do as I want I will circulate this. That was the nature of the coercion," she said.

"He continued to ask him to engage in some sort of sexual activity. That was against his will. He agreed to something referred to as 'The Deal'."

She said the victim went to his tormentor's home and took part in sexual activity with the defendant of the condition it would mean the picture was deleted.

"As is quite common with victims of sexual assaults he blamed himself in many ways. He was ashamed and thought that this would be the end of it," she said.

"But not long after he made further demands.

"He said he still had the embarrassing photographs and he would broadcast them unless he acquiesced.

"He also made a number of threats to the victim and his friends, he said he would 'End him' and would bully his friends."

She said police had spoken to friends who said the defendant was 'very bright' but 'liked putting people down'.

In a victim personal statement the lad said the incidents had a 'massive effect' on him leaving him scared to go to school in his exam year.

The teenager, from Wroughton, admitted two counts of sexual assault, one of sexual activity with a child and one of causing a person to engage in sexual activity without their consent.

He pleaded not guilty to rape and sexual assault on another lad, when he was said to have touched his bottom in a school changing room, which were dropped.

Rob Ross, defending, said psychiatric and psychological reports had been carried out on his client, who had pleaded guilty at the first opportunity.

Deciding not to impose a custodial sentence, Recorder Paul Garlick QC said: "This young man needs careful, careful help and he is not beyond redemption."

He told him: "You do need some help young man. This is a serious matter, I am sure you understand now how serious this is."

He imposed an 18-month youth rehabilitation order with intensive supervision, 20 hours of reparation, and three months night time curfew.

Because of his age and the fact the judge did not imposed a one year custodial sentence the boy will not have to register as a sex offender.