Last year I began to receive calls and emails from Doncaster residents about car thieves.

These were not reports of criminals stealing cars or breaking into cars.

They were about people going underneath cars to do their thieving.

They were after catalytic convertors, and this is the latest type of car theft.

Since 1993, catalytic convertors have been a legal requirement for all petrol vehicles.

They reduce pollutants from exhaust pipes.

Hybrid cars are particularly in their sights as the parts are generally less corroded.

Inside the device, a series of chemical reactions convert noxious gasses into water vapour, which is less harmful.

The thieves unscrew or just hack off the convertors.

It can happen in a matter of minutes, as much in daylight as the dark.

The thieves are not after the devices as such but the materials that make them up.

This is why they will wrench or saw them off if they can’t unscrew them.

The materials in the convertor include palladium, rhodium and platinum – and they are very valuable.

As I write this, palladium is selling at more than the price of gold and platinum at about half.

Clearly, there is a level of sophistication involved in these thefts.

Criminals need to know who they can sell the materials on to.

At the moment these crimes are happening more frequently in other parts of the country.

In those places we can see how quickly a criminal market develops.

So, in 2017-18, for example, the number of such thefts in Coventry was 23, but by last year that had risen to 233.

In London over the same period it went from 154 to 12,483.

So we have been warned.

The police will, of course, investigate and, hopefully, successfully prosecute car thieves.

But this is after the event.

As motorists we should not be doing things that help the thieves.

If we have a garage, we should use it and not leave cars unattended on the drive.

If we don’t have a garage we need to park as close to the kerb or a wall as possible, with the exhaust as near to the barrier as we can get.

The worst thing we can do is park with wheels up on the kerb.

In 2021, I will be asking the police to maintain a focus on car thefts.

But we can all make the job of the thief more difficult.