Police are hunting for a man who exposed himself in Leavesden Country Park.
Hertfordshire Constabulary were called after a woman in her 30s witnessed a man with his trousers down and was exposing himself on Wednesday, May 21.
The woman, who was walking her dog at the time of the incident, then sought help from the park ranger before police were called at 9.50am.
The man is said to be white, of slim build and in his thirties. Police believe that he had a yellow bike covered with bags at the time of the incident.
No arrests have been made.