Two teenage boys arrested in connection with a sex attack at the Derby have been released with no further action being taken against them.

The teenagers, both 17, were arrested in November 2013 but police said yesterday they do not have enough evidence to launch a prosecution.

A teenage girl was sexually assaulted in a field in the fairground area at Epsom Downs Racecourse at 4pm on Derby Day in 2012.

Officers, from East Surrey CID, are supporting the victim, who was 15 at the time of the attack, as the investigation continues.

Detective Sergeant Oana King, said: "The victim has shown real bravery throughout the investigation and for this she must be commended.

"I hope one day we will be able to bring the offender to justice for their crime and allow her to move on with her life."

She added: "Although it is disappointing that we have not yet been able to charge anyone in connection with this incident, this will remain an open investigation and it will be reviewed at regular and appropriate intervals.

"Since the offence occurred, relations between the offender and their friends or relatives may have broken down, and someone who was not in a position at the time of the assault to provide information, may be able to do so now.

"If this is you, please contact us and we will treat your information in the strictest of confidence."

Police said the Crown Prosecution Service (CPS) had considered the file and advised there was not enough evidence to proceed with a prosecution.

Surrey Police "strongly encourages" all victims of sex attacks or abuse, not matter how long ago, to seek help and advice and share information with them.

Anyone with information should call Surrey Police on 101, quoting reference EP/12/2172, or call Crimestoppers anonymously on 0800 555 111.