A registered sex offender used an alias to arrange repeated meetings with a 14-year-old girl and sexually assault her, a court heard.

Gary Cawthorne, 53, from Greenhithe, posed as a Lee Mason to make contact with the girl and promise her a job.

Messages between him and the girl were found on the victim's phone by one of her school friends, who then used another name to contact Cawthorne asking for a job of her own.

He requested a facial photo, which she sent, but upon being asked for a photo of her body the girl reported the conversation to her parents.

They contacted the school, who notified police on February 29. Officers from the Met Police's Sexual Offences Exploitation and Child Abuse Command interviewed the girls the next day and launched an investigation.

Lee Mason was identified as Cawthorne and arrested on March 2 for questioning. He was then arrested again and charged on March 5.

"Cawthorne is a known sex offender and is a danger to children and has totally disregarded the provisions of his SOPO" Detective Constable Tony Foran

During a hearing at Southwark Crown Court, Cawthorne pleaded guilty to two counts of sexual assault on a child under 16, one count of grooming, and one count of breaching a Sexual Offences Prevention Order (SOPO).

He will be sentenced at the same court on Tuesday, May 31.

Detective Constable Tony Foran said: "Cawthorne is a known sex offender and is a danger to children and has totally disregarded the provisions of his SOPO.

"He pursued the 14-year-old girl by phone and in person. Then he sexually assaulted her.

"The victim's friend became suspicious of his contact and thanks to her brave actions she was able to flag up his activities to her parents who then alerted the authorities."

Cawthorne was already a registered sex offender after being convicted of sexually assaulting a 16-year-old girl in 2012.

He then escaped with a caution for molesting a 20-year-old woman at London’s Grand Hotel just three months later.