The rock hit the windscreen of a black convertible Citreon DS3 being driven along Honeybourne Way at around 2.25pm on Thursday 4 April.

"It was believed that a teenager who was in a group had thrown the item," Gloucestershire Constabulary said in a statement.

Authorities are now appealing for witnesses to help identify the person who threw the rock.

"There were other motorists and members of the public around at the time of the incident, including people who were walking along Millennium Bridge, and may be able to help identify the person who threw the rock," police added.

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Police called on parents to speak to their children to establish if they were around the area and to warn them "of the dangers of this type of behaviour."

Gloucestershire Constabulary released images showing the damage caused to the car.