Almost the entire male population of two neighbouring villages is to be asked to undergo DNA testing as police step up their hunt for a killer.

Detectives investigating the murder of bachelor David Williamson are widening their search, almost eight months after the 58-year-old was found lying unconscious by the side of a quiet country road.

Police believe he was struck on the back of the head by a blunt instrument as he walked home from a party at his local pub in Huby, near Easingwold, North Yorkshire, on March 25.

Forensic examinations have produced a DNA profile, which detectives believe is that of the killer, but the investigation has so far failed to find a match. Now, in a dramatic new move, all males over the age of 14 who are living in Huby and nearby Sutton-on-the-Forest - a combined total of 800 - are being asked to volunteer for DNA tests.

Samples have already been taken from 100 men whom police know had been in contact with Mr Williamson in the 36 hours before his death.

Detective Chief Inspector Nigel Boynton, who is leading the inquiry, said: "This is an extension of the tests we have already made and I am hopeful that these new results will take us closer to finding David Williamson's killer.

"People in the two villages have been very supportive of the murder inquiry and it is my hope that they will continue to help by coming forward in numbers to take part in this screening programme."

The voluntary testing starts in Huby on Monday and in Sutton-on-the-Forest the following week.

Mr Williamson was discovered by the side of the road not far from his home in Sutton-on-the-Forest early on March 26. He died later in Leeds General Infirmary.

Two appeals have already been made on the BBC Crimewatch programme and several anonymous callers phoned in to offer detectives the same name of a possible suspect.

There is also a £5,000 Crimestoppers reward for information leading to the capture of the killer.