A man was seen masturbating while hiding in some bushes in St Albans' biggest park.
Police are trying to trace a man who was committing a sex act on himself at Verulamium Park on Tuesday afternoon.
The man was seen by passers-by, including children, in the bushes by the Roman Wall by King Harry Lane between 3.30pm and 6pm.
He is described as a man aged in his late 30s to mid-40s with dark hair.
It is believed he was wearing a blue shirt and light brown chinos.
PC Dawn Rust from the St Albans Safer Neighbourhood Team said: “This happened just after the end of school yesterday and later into the afternoon.
"If you saw this man or know who he may be, please get in touch. No-one should have to be exposed to this kind of behaviour.”
Anyone with any information is asked to contact police on 101 quoting reference 41/0583/19.
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