Police have warned car and van owners to be vigilant after a sharp increase in motor vehicle crime over the last year.
Since April 2018 there have been 239 offences recorded by police in Dacorum.
That is up from 187 offences over the same period 12 months earlier – a rise of 28 per cent.
Thieves often target homes for keys which have been left close to letterboxes or insecure windows and doors, enabling them to drive the vehicles away.
Thieves are also employing special equipment which can hijack the signal from keyless entry fobs that are left inside the home close to where the vehicle is parked.
The equipment can be used to unlock the vehicle and even start the engine.
Insp Andrew Palfreyman said: “Criminals are evolving their tactics all the time, using technology to bypass security systems.”