Two police officers have been removed from operational duty after a pensioner complained that they smashed his car window and kicked his windscreen.
One used a baton to repeatedly hit the driver-side window of 70-year-old Robert Whatley's Range Rover as the other officer stood on the bonnet.
Whatley, of Usk, Monmouthshire, was convicted of failing to wear a seatbelt and to stop, and of having tinted windows not conforming to legal requirements. He was cleared of failing to stop after an accident.
He was reportedly followed for 17 minutes after driving off while Gwent Police officers issued him with a fixed penalty notice.
The court heard he drove away because he thought he had been dealt with and needed his medication for a heart condition and a stroke, the Western Mail reported.
Whatley, who stayed within the speed limit during the pursuit, thought the police car following him was sounding its siren and had its blue lights on because it was escorting him home.
He pulled over when confronted by a police stinger device on the road into Usk, the paper said.
Footage of the incident, filmed from the police car and published online by the Western Mail, shows an officer running towards Whatley's black 4x4 and breaking the window when it stops on a country road. Whatley is dragged out about a minute later.
Another officer climbs onto the bonnet and appears to kick the windscreen.
A two-day trial at Caerphilly Magistrates' Court heard claims from an officer that Whatley was aggressive during the incident last September, the paper reported.
He admitted having a registration plate which did not meet regulations and was fined a total of £235 and ordered to pay £300 prosecution costs.
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Ifti Manzoor from law firm Irwin Mitchell said: "The actions of the police officers in smashing the side window and jumping on the bonnet seem excessive considering the circumstances and we welcome the investigation.
"I act for many individuals whose safety has been compromised in similar circumstances by the police and Mr Whatley should obtain expert legal help to ensure justice is done."