With increasing numbers of thefts of satellite navigation systems, drivers have been advised to security mark their in-car possessions in order to avoid having to make a claim on their insurance policy.

Marking sat-nav systems in such a way not only makes them less attractive to would-be thieves, but also makes it easier for the police to identify their rightful owner in the instance of a theft.

Given the rising number of cases of the crime, police in Dereham, Norfolk are set to offer a free-security marking service to sat-nav equipment owners as part of the nationwide Safer Stronger Communities Fund initiative.

"Security marking your property is a good crime prevention strategy because marked property is hot property," said Dereham crime prevention officer PC Gail Kevern.

"It reduces the value of the stolen goods for thieves and deters thieves but also makes it readily identifiable should it be stolen and later recovered."

Recent research by the satellite navigation company Becker found that lost motorists account for 325 million wasted miles travelled by car each year, with drivers unfamiliar with an area and its roads more likely to end up having to claim on their motor insurance policy.