A 13-year-old boy has been found guilty of sexually assaulting a five-year-old girl.

The boy, from Mitcham, who cannot be named for legal reasons, was found guilty of two counts of sexual assault at Wimbledon Magistrates youth court on Monday (June 11).

During a three-day trial, the court heard how the boy, who was just 12 when the allegations were made in March last year, was initially accused and charged with rape after taking the girl to the bathroom while she was in the care of his mother at their Mitcham home.

The two charges of rape were later withdrawn and reduced to sexual assault.

In court, the girl’s father said: "I asked her what had happened.

"She started and was mumbling at first and I asked her what did [he] do to you?"

The child then explained the sexual assault, the dad said.

In a police interview played in court, the boy was asked if he knew what sex was, to which he said: "When you have babies."

When asked if he knew what rape was he said: "When you force someone to do it."

He also confirmed he had received sex education classes at school.

A medical examination carried out on the girl 14 days after the alleged assault revealed no abnormalities but giving evidence in court Dr Benedicta Ogeah, paediatrician at Queen Mary's Children's Hospital, did not rule it out.

She said: "It is possible to have sexual assault and have normal findings."

She added: "[The girl’s] behaviour in my view was that there was psychosocial trauma that needed to be followed up and managed."

The boy was released on conditional bail for sentencing at Lavender Hill Magistrates' Court next month.