Thieves are stealing catalytic converters from cars parked in a hospital car park.

Hertfordshire Constabulary says there has been a recent spate of thefts of the devices from the staff car park in Watford General Hospital.

It comes after figures obtained by the Observer showed 20 of the devices were stolen in Watford between August 8 and September 19 in 2019 - that number had only been two during the same time frame in 2018.

Police have put the thefts of the devices down to thieves targeting the precious metals the catalytic converters contain, which include platinum, copper and nickel.

In response to thefts of the devices from cars at Watford General, police will be providing free catalytic converter markings at Vicarage Road Service Station for hospital staff who own a hybrid car.

Watford Police wrote on their Facebook: “We have seen a large increase in Theft from Motor Vehicles in the recent months whereby hybrid vehicles, usually parked in Public Car Parks, are being targeted specifically for their catalytic converters.

“The price of metal has increased in recent times with hybrid vehicles containing higher levels of valuable metals.”

The purpose of a catalytic converter is to clean up harmful gases from the car engine before they exit the exhaust pipe.

In September 2019 the Steven Eagell Toyota garage in Ascot Road, Croxley Green said it was struggling to deal with the number of people coming in for replacements of the stolen devices.

It said second and third generation Toyota Prius' and second generation Auris' which were the cars to mainly be targeted.

Toyota explained the increase in reported thefts had made it difficult to provide the needed parts and were taking “urgent” action to address the problem with suppliers.

Watford General staff can have their catalytic converters marked between 9am - Midday on Saturday, January 11 and 9am - 2pm on Wednesday, January 29.