Thames Valley Police is appealing for witnesses after a man exposed himself on Saturday.
At around 3.30pm, the victim, a 33-year-old woman, was jogging around Furzton Lake when a man blocked her route over a bridge with his bike and exposed himself.
The man was distracted by a member of the public, who was walking his dog, and the victim ran past the offender and rang the police.
PC James Punter, of Milton Keynes police station, said: “I would like to appeal to anyone who has information about this man or may have seen a man acting suspiciously in the area around the time of the incident.
“I am keen to identify an elderly gentleman who had a white “Scottie” dog with him along the Loughton Brook area of Furzton Lake. This gentleman leashed his dog to allow the victim to pass him moments before the exposure.
“There were a number of people who the aggrieved ran past just after the incident.”
The man is described as white, aged between 18 and 21-years-old, between 5ft 6ins and 5ft 9ins. He is of large build and has short chopped fair hair. He was described as wearing a plain grey hooded top with large white drawstrings and pale blue/stone washed baggy jeans. The bike was described as not being noticeable and believed to be either a grey or silver Mountain bike with straight handle bars.
The victim was wearing black running trousers, an orange and black vest, a blue jacket around her waist and a black beanie hat.
If anyone has information about this incident please contact PC Punter via the new 24-hour non-emergency single number 101. If you do not want to speak to the police, call the Crimestoppers charity anonymously on 0800 555 111.