A teenager who engaged in consensual sex acts with a 13-year-old girl after lying to her that he was 15 has been sentenced to two-and-a-half years' youth custody.

The girl initiated the intimacy with Marcus Petrie, which happened on a single occasion at her home, Maidstone Crown Court was told.

Contact between them ended after she found out his true age was 19. She later told police she gave her consent to the sexual activity.

Prosecutor Paul Jackson said the pair met in Gravesend last year and they later went to her home in Medway. They ended up in her bedroom and began kissing.

The girl pulled down Petrie trousers and performed a sex act on him. He touched her intimately.

“She said she wanted to do this,” said Mr Jackson. “She confirmed that nothing had happened since. She told him she was 13. He told her he was 15. In fact, he was 19.

“Shortly afterwards she discovered his real age. She confronted him about it. He asked her if she was going to report it to the police and threatened to kill himself.”

When arrested, he denied there was any sexual contact.

Petrie, now 20, of Cypress Grove, Elvington, near Dover, admitted causing or inciting a child to engage in sexual activity and sexual activity with a child.

Judge Charles Macdonald QC heard Petrie’s only brush with the law had been a reprimand for stealing a bicycle.

Thomas Daniel, defending, said it did not take a great deal of imagination to understand why the girl thought Petrie was only 15.

“He does not look his age or necessarily act it,” said Mr Daniel. “He lied about his age out of embarrassment. He is most ashamed.

“She accepted she initiated sexual contact. He says he knew it was wrong and should have stopped it. His mother says she still can’t see what he did wrong. There was no grooming or planning.”

Mr Daniel submitted that a probation report recommendation for a suspended sentence could be followed. It stated Petrie might not be able to cope in custody.

Judge Macdonald said: “The law exists to protect children. It doesn’t really matter what the complainant’s attitude was.”

“He lied about his age out of embarrassment. He is most ashamed..." - Thomas Daniel, defending

He told Petrie: “There was consent throughout but, of course, no consent in law.”

He added: “There is clearly some mitigation here. You are of good character and I accept you are remorseful.

“More importantly, I am satisfied there is in your case, partly because of a difficult background, a lack of maturity which has affected your responsibility for this offence to some extent.

“They remain, nevertheless, serious offences. The law exists to protect her from this.”

The judge said he had decided that because of Petrie’s immaturity he could go outside the range of sentences, but added it had to be immediate custody.

Petrie’s name will appear on the sex offenders’ register indefinitely and he was barred from working with children or vulnerable adults. A sexual offences prevention order was made.