A teenager who stabbed two south London schoolgirls and sexually assaulted four others had an"obsessive interest" in violent pornography, a court heard.

The terrifying series of random attacks - the first of which when the boy was just 14 - happened over a 12-month period in Thornton Heath.

He acted on “urges” to live out the fantasies he had watched online, Croydon Crown Court heard.

The teen, who cannot be named for legal reasons, had pleaded guilty to four counts of sexual assault, two counts of wounding with intent, common assault, and assault by penetration at a hearing in April.

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He appeared for sentencing on Friday (July 16) after a previous hearing was postponed after he contracted coronavirus.

Caging him for a minimum of four-and-a-half years, a Judge told him that he represented a "very high risk of reoffending."

Detectives only linked four similar incidents last Autumn with previous attacks in November 2019 because he could not prey on girls as they walked to school because of the pandemic.

In the second most recent attack, just before 9am on November 4 last year, a schoolgirl was attacked from behind and stabbed in the leg.

Two days later, at around 8.20am, a 15-year-old girl was stabbed in the arm from behind just a 10-minute walk away.

Both girls were treated at the scene by paramedics before being taken to the hospital where their conditions were deemed not life-threatening.

The victims went to different schools and Scotland Yard said it is not thought the victims knew each other.

In an earlier attack, on September 2 last year, a mum was punched in the face when her 13-year-old daughter was sexually assaulted in front of her as the fiend to remove the girl's underwear.

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Claire Harden-Frost, prosecuting, told the court: "He was caught after a significant police investigation focused on CCTV obtained from local businesses and residents and a chance accident causing him to lose his blood on one of his victims.

"The evidence collated by the police during their investigation showed [he] would leave his address early in the morning, often before he needed to do so before he had to go to school, and roam the streets of Thornton Heath looking for young girls.

"If he found one to his liking he would sexually assault them. In later offences, he would carry a knife and used it to carry out one of the sexual offences. In counts eight and nine he simply stabbed his victims.

"These victims were all strangers. They didn't know [him] and had not caused him any harm.

"Alarmingly, the fact they were walking with friends or even a parent did not deter [him]. He simply would attack them.

"He took advantage of the local area and simply disappeared.

"Analysis of [his] phone shows he was forensically aware and took care to make sure he was not recognised.

"He changed the way he wore his hair and had his hood up and often wore dark clothing. This worked to a certain extent.

"None of his young victims were able to identify the preparator. One of the witnesses who saw the last stabbing even believed he was a girl."

Cathy Ryan, in mitigation, said a psychiatric report did not find any condition that predisposed the teen to commit these attacks.

She said: "There is a broad consensus that [this defendant] committed these attacks after a combination of social isolation, victimisation and extreme pornography.

"His mother would not be the first mother of a young teenager concerned he would be affected by gang culture.

"It is a damned if you do, damned if you don't situation where you're not safe if you're inside or outside of the gang.

"She took a supervisory role in his upbringing, often escorting him and not allowing him out in the evening, afraid of him falling into the wrong crowd.

"What she did not supervise as much was his access to the internet and that became by default his principal activity.

"Isolating [the defendant] from his peers forced him increasingly into his own company and the internet. This had been aggravated by bullying at school."

She added: "There is literally no kind of pornography, violent pornography that an average computer literate schoolboy cannot access.

"It's not hard to imagine the effect this material would have on the mind and the emotional development of a youth who had no experience with the opposite sex and was still in the process of achieving empathetic maturity.

"Exposure to the utterly dehumanising effects of pornography at the age of 11 led to his complete failure to recognise female counterparts as human beings like himself."

She continued: "He described to the [youth offending teams] worker feeling angry and he experienced release after the attack.

"It's interesting to note that this relief did not manifest itself on the last attack, but in its place felt instant regret. Perhaps this is some sign of change of thinking already."

Judge Nicholas Ainley passed concurrent sentences to run together and ruled the defendant would be sent to a detention centre for a minimum of four and a half years and, if eligible for parole, will be on license for a further three years.