A police chief has spoken of the rocketing number of thefts in Cambridgeshire of catalytic converters.

Supt James Sutherland warned many contain “precious amounts of metal” which make them a target for thieves.

“You are basically talking about the value of a reasonably priced engagement ring being stuck to the underneath of your car,” he said.

“And thieves are pretty determined to get to it.”

There have been 446 such thefts across Cambridgeshire between January and August of this year.

Supt Sutherland urged people to call police if they see something suspicious.

He said, for example, it might be you see someone looking as if they are working on a car at night – something that wouldn’t normally happen.

“But we see a lot of these offences during the daytime too,” he said.

Popular spots for thieves were often park and ride car park where thieves try and disguise themselves as mechanics, don high viz jackets, and appear to be working on a broken down car.

“It is rare for a car to be jacked up in a park and ride and if you have suspicions, then call us,” he said.

He said police would never be concerned about a false alarm call in such circumstances.

“If everything turns out to be fine, that’s ok with us,” he said.

Supt Sutherland said car owners need to ensure they try and park off street or in a garage. If that’s not possible he urged people to at least park beneath a light or in a well lit spot.

“These criminals are quite determined,” said Supt Sutherland. He said car owners could get specific products to help protect their vehicles and he said garages could provide assistance.

Supt Sutherland said older, and often Japanese, models were prime targets since the catalytic converters on them contained more precious metals than more recent models.

“If you have an older model, it is well worth investigating specialist options,” he said. “You can get very secure covers to go over them and make it much harder for people to go under your car. They also act as deterrent.

Catalytic converters are found in the exhaust system of every car and reduce the output of toxic gases and pollutants.

Stealing them has become popular because they aren’t easily identifiable and can be sold on for the precious metals found inside them which can fetch between £50 and £200 a time.