A registered sex offender and former Met Police officer from Greenhithe, who is a “danger to children”, has been jailed for more than four years after admitting to grooming and sexually assaulting a 14-year-old girl.

Gary Cawthorne promised the “vulnerable” young Londoner an admin job in a fictional property business and took the opportunity to assault his victim during their so-called business meetings.

As soon as they were alone he offered her £300 to “get into her knickers”, the Daily Star reports.

On another occasion he groped her breast at a car wash in Ebbsfleet.

The 53-year-old used the alias of Lee Mason and his crimes only came to light with the schoolgirl’s suspicious friend contacted Cawthorne, who used to live in Plumstead, to inquire about a job.

The sex pest asked for several photos and the girl sent a head shot – but declined requests to send further images of her body.

The teenager told her parents about the messages and they contacted her school.

Both girls were spoken to by officers from the Sexual Offences Exploitation and Child Abuse Command on Tuesday, March 1.

Cawthorne was soon identified of the sender of the messages, and arrested the next day. He was charged on March 5.

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Southwark Crown Court

The paedophile pleaded guilty to two counts of sexual assault on a child under the age of 16, one count of sexual grooming, and breach of a Sexual Offences Prevention Order at Southwark Crown Court on May 3.

He was jailed for four years and five months at the same court yesterday (May 31).

Southwark heard that Cawthorne was already a registered sex offender – having been convicted of assaulting a 16-year-old girl on October 24, 2012.

Three years ago, Judge Loraine-Smith expressed fury that Cawthorne had escaped with a caution for molesting a 20-year-old cleaner in his home, whilst on bail for attacking the young victim.

Cawthorne told the teenager he worked for top agencies including Select Model Management and ordered her to strip so he could measure her before cupping her breasts, Southwark heard.

He advertised himself on Gumtree and Judge Loraine-Smith described Kent Police’s decision to caution Cawthorne as “extraordinary”, Mail Online reported at the time.

Detective Constable Tony Foran from the Met's Sexual Offences, Exploitation and Child Abuse Command said: “Cawthorne is a known sex offender and is a danger to children - he has now been jailed for his offences.

“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.”

The paedophile got two years in jail for sexual grooming, a further two years for breaching a Sexual Harm Prevention Order, and five months for two counts of sexual assault on a child under the age of 16 – to run consecutively.