A 15-year-old girl was subjected to a serious sex attack by a teenage boy at the Epsom Derby, police have disclosed.
The victim has told officers she was attacked in a nearby field by a boy she met in the music and fairground area at the racecourse.
The Queen chose the Epsom Derby on Saturday to start the national Diamond Jubilee celebrations marking her 60-year reign as monarch.
Surrey Police said the sex attack is believed to have happened at around 4pm and was reported to officers just after 6pm the same evening.
Some race-goers have been spoken to by police who appealed for the public's help in tracing the attacker, described as aged between 16 and 17.
Detective Inspector Oana King, of Surrey Police, said: "This was obviously a very traumatic experience for the young girl involved.
"Thankfully this kind of offence is extremely rare and I would like to reassure members of the public that we are doing all we can to identify the perpetrator and bring him to justice.
"We have already spoken to a number of people who were at the Epsom Derby event but are keen to speak to anyone else who may have seen the suspect prior to or after this offence."
Police said they were keen to trace a woman who reported the attack to a member of St John's Ambulance staff after she overheard a conversation about it.
Ms King added: "This woman did the correct thing by reporting her concerns after overhearing a conversation about this incident but unfortunately she left the area before our officers were able to speak to her.
"I would urge this woman to come forward as she may have vital information which could assist the ongoing investigation."
The suspect is white, of skinny but muscular build, with a prominent wide jaw line, short gingery-blond hair and a pale, spotty complexion.
He was wearing a long-sleeved, dark blue top and baggy blue jeans. He was with a boy of a similar age, of a bigger build, with short, flattened, brown hair and tanned skin. He was wearing a white, short-sleeved top and blue baggy jeans.
Anyone with information is asked to call Surrey Police on 101 or Crimestoppers on 0800 555 111.
