At around 10.45pm on 29 August a woman heard the sound of metal grinding outside an address in St Martin’s Square in Gillingham. She looked outside and saw two men wearing dark clothing and balaclavas standing by two parked cars.

Another resident went outside and saw a third man crouched down looking at one of the cars. He challenged the offenders and one walked toward him brandishing a metal pole and, as he turned away, he was struck on the back with the pole.

The victim, aged in his 50s from London, sustained a red mark across his back.

It was later discovered that the catalytic converter of a Volvo car had been stolen.

The first offender is described as white, around five feet six inches tall, of medium to stocky build. The second offender was slightly taller, but of a similar build. They both wore black clothing and a black balaclava with white or silver around the eye holes.

The third offender wore a dark grey hooded top.

PC Kier Dagnall, of North Dorset police, said: “This was an unpleasant incident for the victim and I am appealing to anyone who witnessed any suspicious activity at the relevant time, or knows who was responsible, to please contact Dorset Police.

“Incidents of catalytic converter theft has increased in Dorset over the last year and there are a number of steps motorists can take to reduce the chance of becoming a victim.”

Tips include:

• Think about where you park: if you can, park your vehicle in a locked garage. If this isn’t an option, then park it in a well-lit and well-populated area. Park close to fences, walls or a kerb and avoid parking your vehicle half on the pavement and half on the road, as this may make it easier for thieves to access the catalytic converter. If you are parking in a public car park, consider parking alongside other vehicles. This will make it harder for thieves to get close enough to get underneath the vehicle.
• Mark your catalytic converter: you can mark your catalytic converter with a unique code that will relate back to your vehicle. This is done using SmartWater and is an incredibly effective way of preventing theft. SmartWater is a forensic liquid, which can withstand heat of up to 600 degrees. It can be applied to car parts and each batch has a unique code which allows it to be traced back to the owner.

Anyone with information about this incident is asked to contact Dorset Police at www.dorset.police.uk, via email 101@dorset.pnn.police.uk or by calling 101, quoting occurrence number 55210139804. Alternatively, to stay 100 per cent anonymous, contact the independent charity Crimestoppers online at Crimestoppers-uk.org or call Freephone 0800 555 111.