Three teenage girls were spied on as they were changing at a leisure centre.

The girls were in a changing room of the William Penn Leisure Centre, in Rickmansworth, on January 15.

At 8pm one of the girls noticed a mirror being pushed under the cubicle.

PC Chris Gottmann said: “I am appealing for anyone else who may have witnessed someone behaving suspiciously within the changing area around the time stated to come forward.

“If you do see any suspicious activity in the future please inform the leisure staff immediately.

“I would like to reassure the public that we are doing all we can to trace the person responsible as a matter of urgency.”

Anyone with information should contact Hertfordshire Constabulary on 101.