A driver who successfully challenged the accuracy of a police speed gun has told of his relief at overturning his conviction.

Brian Wiltshire, 48, was yards from his home near Caton, Lancaster, when he was clocked at the roadside travelling 39mph by an officer using a hand-held device.

He was adamant that he was only going between 25mph and 29mph in the 30mph zone and contested the reading.

The conviction was overturned after technical experts explained laser guns could return faulty readings if the equipment was not set up properly.

The decision by a judge at Preston Crown Court could pave the way for similar challenges from speeding motorists.

Mr Wiltshire was driving home in his M-reg Escort nearly a year ago when he was pulled to the side of the road by officers using a LTI 20/20 laser device.

Facing a ?60 fine and three points on his licence, the designer clothes shop owner pleaded not guilty to the offence before magistrates, but was convicted last June.

He refused to accept the ruling and took the case to Preston Crown Court.

A judge allowed his appeal after hearing expert evidence that laser devices can give faulty readings if they are not aligned properly.

His lawyers argued he had no case to answer because the officer operating the device had not done the correct checks beforehand.

However, Judge Andrew Woolman indicated the ruling did not set a precedent and will give a full ruling on his decision on a date yet to be fixed.

Mr Wiltshire said he felt vindicated following the appeal ruling.

He said: "Initially I thought I was being pulled over in a routine check but was shocked to learn I had supposedly broken the speed limit.

"I was stopped in a built-up area at a time when the schools were finishing for the day and I was certain that I was going under 30mph.

"I tried to speak to the officers involved and tell them the equipment must be wrong but they weren't having any of it."

He added: "Although the judge has not explained his ruling I believe it shows that such laser devices can be wildly inaccurate.

"It is worrying that an experienced police officer wrongly thought he had carried out the proper checks.

"He may have been just following the training he had received. "I wouldn't want every Tom, Dick and Harry to appeal against a speeding fine but people should be made aware that it is worth pursuing if they are convinced they did not break the law."

Jeanette Miller, senior partner at Manchester firm Geoffrey Miller, who defended Mr Wiltshire, predicted the decision could lead to more challenges.

She said: "It makes you think how many other drivers have been wrongly accused or wrongly convicted due to police officers not testing the laser equipment properly before using it."

A spokesman for Lancashire Police said: "We remain confident with the use of the equipment and its reliability.

"In this instance the case was lost because an officer failed to carry out an administrative function."