Essex Police is at the forefront of launching a national campaign to tackle illegal metal detecting which could deprive the county of important historical artefacts and treasures.

Operation Chronos sees the police team up with Historic England and other partners to urge land owners to report the practice, known as "nighthawking”, where people go on to farmland, archaeological sites and other areas of interest to find and steal coins and other artefacts for their historical and financial value.

The practice can damage farmland, disturb wildlife and destroy archaeological sites.

Nighthawkers will enter land with metal detectors and without the permission from the farmer or other land owner and usually at night.

All finds removed by them whilst trespassing may amount to theft.

Coins and artefacts found by nighthawkers are usually kept in private collections or sold for personal gain.

Because the objects are stolen property, nighthawkers are unlikely to report their finds, leading to valuable historic data being lost for good.

Counties like Essex are particularly vulnerable to this crime due to the rich heritage and large amounts of arable land in these areas.

Assistant Chief Constable Julia Wortley, Essex Police lead on Territorial Policing, said: "So-called nighthawkers might think they’re no different to people who go metal-detecting for a hobby, but their actions damage the countryside, threaten our heritage and lead to the loss of important and invaluable national artefacts simply to satisfy the greed of a small group of criminals.”

Pc Andy Long, Wildlife, Heritage and Environmental Crime officer, said: "Most people who metal detect as a hobby abide to the law and codes of practice and have a love of the outdoors and history, respecting farmland and other surroundings.

"Nighthawkers seriously damage that good reputation.

"We are asking land owners and people in rural areas to gather evidence by taking registration numbers of vehicles and descriptions of those involved, and pass these details to the police immediately by calling 101.

"We would urge people not to approach nighthawkers as you may be placing yourself in danger if they become aggressive.”

Mark Harrison, National Policing and Crime Advisor for Historic England, said: "The practice of nighthawking is an issue that we take very seriously.

"We recognise that the majority of the metal detecting community comply with the laws and regulations relating to the discovery and recovery of objects from the land.

"However, just as it is against the law to break into someone's house and steal their possessions, so it is illegal to damage land and steal valuable historical artefacts.

"We are working hard with the police service at a national and local level to identify the criminal minority who operate outside of the law”.

Landowners are advised that evidence of nighthawking includes:

• Finding holes dug in fields with no obvious explanation why they are there

• Footwear marks

• Vehicle tyre marks

• Cigarette butts

• Drinks bottles/cans

• Other discarded items.

Operation Chronos will be effective as of today, Monday July 20.