He spots his prize, smashes a window and snatches a £350 satellite navigation system all in just over 10 seconds in the latest craze among crooks.

Images from a motorist's private security cameras show, car thieves are now targeting valuable 'must-nick' Sat-Nav systems and snatching them with the minimum of fuss.

Not even the presence of the two cameras, installed by vehicle owners Lindy Jones and Darrell Ballantyne, detered this brazen thief and his accomplice.

Sgt Nick Garside, of Thames Valley Police autocrime team, said the first Sat-Nav theft recorded was in February and since then another 108 have been stolen across the county.

He said: "Sat-Navs are today's laptops. Laptops were the 'in thing' about four or five years ago, and car radios before that."

Mrs Jones's son, Henry, 16, said he could not believe how quickly the thief struck outside the family home in Oxlip Leyes, Bicester.

The Gosford Hill School pupil said: "This guy does it in about 10 seconds. We are the fifth people around this area to have it done in the past couple of months, and the second in two days."

The footage shows the thief and his accomplice, believed to be a woman, walk up to the vehicle. The thief goes to the driver's side first but then comes around to the passenger side and peers in.

As these pictures show, within 10 seconds of spotting the gadget, he tries the door, smashes the window, reaches right in and legs it.

Mrs Jones said she installed CCTV cameras on her house about six months ago after one of their neighbours had a firework thrown through their letterbox.

Last night Thames Valley Police spokesman Tim Wiseman appealed for motorists to take their Sat-Navs out to thwart the thieves.

"Theft from vehicles is a major issue for the force, with members of the public not heeding simple crime prevention advice which results in a high number of opportunist crimes," he said.

"Leaving any valuables in the car is a serious risk, however, the growing use of Sat-Nav systems is creating another new target for these criminals along with laptops, iPods, CDs, cash and mobile phones.

"Across Oxfordshire opportunist criminals are taking advantage and crime rates are increasing, while the police continue with high-visibility patrols and targeting of known offenders through intelligence-led operations."