DETECTIVES investigating a shocking sex attack on a schoolgirl have made another appeal for clues into the case.

A 15-year-old girl was groped by a pervert as she walked along Elgar Road, Reading, shortly after 7am on March 7.

The man approached her from behind and and exposed himself before grabbing her inappropriately.

However, he was startled by a passer-by who shouted at him, causing him to flee.

Detectives investigating the case are yet to track down the Good Samaritan and have urged him to come forward.

A spokesman for Thames Valley Police said: "The victim had been walking down Elgar Road, Reading, by the junction of Waterloo Road at about 7.20am on March 7 when a man approached her from behind and touched her bag, causing her to turn around.

"A passer-by saw this and shouted out. This startled the offender who ran off along Waterloo Road, away from Elgar Road."

The pervert was described as a white man aged in his thirties and between 5ft 6ins and 5ft 8ins tall.

He had short dark hair and was wearing a grey hoodie and blue jeans.

Steve Jennings, investigating, added: "This is a serious offence and we are very keen to identify the man who witnessed this incident and startled the offender.

"The unknown key witness is described as being an Asian man who was about 6ft tall. He had short dark hair, a full beard and moustache and was carrying two shopping bags.

"It is possible that he lived locally to where this offence was committed.

"We would like this man and anyone else with information to call police on 101, quoting reference number 43180069609."